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Journal of the Chemical Society,Faraday Transactions IISSN 0300-959Journal of the Chemical Society, Faraday Transactions ISUBJECT INDEX-VOLUME 73, 1977AAbsolute Rate of the Reaction of C1(2P) with Molecular Hydrogen from 200-500 K (Lee,Michael, Payne, Stief & Whytock) .Absorption and Emission Studies of Solubilizat'ion in Micelles. Part 4.-Siudies 'on &tionibMicelles with added Electrolyte and on Lecithin Vesicles: Excimer Formation and theHam Effect (Dorrance & Hunter) . .Characteristics of 2,3-Dicyano-p-hydroquinone: Effect of pH' on the Emission 'and (Brown& Porter) .Spectra and the Specira of ;he Photoreduced States of khodamine B and Rhohamine 1 lo':Triplet-Triplet (Dunne & Quinn) . .Spectra of Radical Ions of Polyenes of Biological Gterest' (Lakerty, Roach; Sinciair, Tiuscot;& Land)Abstraction from Substiiuted Phenols by Polyvinyl Adetate Radicals in Vinyl Acetaie : Evidenckfor Tunnelling: Isotope Effect in Hydrogen Atom (Simonyi, Fitos, Kardos, KOV~CS,Lukovits & PospiSil) ..of Chlorine Atoms by Cyclohexyl Radicais from CHClzCN and CHiClCN: Effect okCyano-group Substitution on Rates of Metathetical Reactions. Part 2.- (Gonen,Horowitz & Rajbenbach)Acceptor: Self Associated Donor Equilibrium': Eledtron Spin Resonance Study' of the 1 : 1Hydrogen-Bonded Complex of Di-t-Butylnitroxide with Methanol. An Analysis of an(Bullock & Howard) . . .Acetate Anions: Proton Chemical 'Shifts' of Hydrogen Bonded Complexes of Acetic' Acid.Electric Field Calculations for the Monomer-Dimer Shift and for Complexes with Fluorideor (Akitt) ..[2H4] Acetic Acid'on t d Rutiie: Inirared Stud; of the Adsorption of (Griffiths &'Rochester)'Acid-base Catalysis. Part 1 .-Catalysis of the Hydrolysis of Acetaldehyde Dimethyl Acetal(1, 1 -Dimethoxyethane) by Methacrylic Acid-divinylbenzene Copolymer (a weak-acidion-exchange resin), and the Characterisation of Polymer Catalysts : Heterogeneous(Gold & Liddiard)Part 2.-Catalysis of the Hydroiysis of Ethyl Vinyl Eiher (ethoxyethene) by 'MethacrylicAcid-divinylbenzene Copolymer Weak-acid Ion Exchange Resins : Heterogeneous(Gold, Liddiard & Martin) . . .Acidic Properties of Silica-Alumina Gels as a' Funciion of Chemical' Composition : InfraredApproach: Evolution of the (Scokart, Declerck, Sempels & Rouxhet) .Properties of Silica-Alumina Gels as a Function of Chemical Composition.Titration andCatalytic Activity Measurements (Damon, Delmon & Bonnier) .Acridine: An Investigation of its Molecular and Crystalline Photophysicai Behaviou;(Williams & Clarke) .Activated Chemisorption. Part 2.lTheo;eticai Models : Kinetic's of (haroni & Ungarish) *Chemisorption Part 3.-hmount and Distribution of Adsorbate at Varying Temperatures andInsertion Products : Reaction of Singlet Methylene with Methylenecyclopropane. Part 2.-High Energy Reaction Pathways for Chemically (Clements, Frey & Walsh). . ..Energy: Kinetics of Electron Transfer Reaction between Manganate and Permanganate Ions.Enthalpy of Diffusion for Iodine in Mixed Solvents (Nakanishi & NishimotojActive Site and Mechanism for Alkene Isomerization in Cur1 Exchanged Y-Type Zeolite:.Activities of Olefinic Derivatives as Components' of Photoinitiating System; based onActivity Coefficients in Binary n-Alkane Mixtures : Prediction of Infinite Diluhon iLaub;Adamantanes: Order-Disorder Transitions in Substituted (Clark; Knoi, Maikle & McKerveyjAdhesion at Liquid-Liquid Interfaces and the Relationship to Salt Desorption: Work andAdsorbed on 7-Alumina.Part 1.-Development of Sites Active in Energy Transfer: y-Pressures: Kinetics of (Aharoni & Ungarish) . * . . . .Activation Energies of Reactions that are almost Diffusion-controlled : Arrhenius (Logan)Calculation of Rate Constant and (Dolin, Dogonadze & German) .. .Determination of the (John & Leach) Electron Spectroscopic Study of Nitrogen Species (Matloob & Roberts) 1 1394 SUBJECT INDEX-VOLUME 73, 1977on Goethite (a-FeOOH) : Infrared Spectra from Binuclear Bridging Complexes of SuIphateon Graphite at 77 K: Caiorime'tric Evidence for a Bidimensional Phase Change 'in theMonolayer of Nitrogen or Argon (Rouquerol, Partyka & Rouquerol) . . . .Adsorption and Oxidation of Dimethylaniline by Laponite (Vansant & Yariv) . . .from Solution: Effects of Ionisation on (Rendall & Smith)Model : Determination of the Surface Heterogeneity of Solid Particuiates using the Pat'chwise(House & Jaycock) . . . . .of [*H4] Acetic Acid on to Rutiie: Infrared'Stud; of (Griffiths & Rochester) ..of Carbon Monoxide by Nickel: Infrared Study of Effects of Sulphur-poisoning on thk(Rochester & Terrell) . . .of Gases on Solids: Alternative t'o the'EIovich Equation for ;he Kinetics' of (Ritchie)of Hexafiuoroacetone on to Rutile: Infrared Study of the (Griffiths & Rochester) .of Sulphur Compounds on Silica and Silica-supported Nickel: Infrared Study of the(Rochester & Terrell) . . . . .of Water on to the Surface of Rutile: Infrarid Study of'the (Griffiths & Rochester) . .on Energetically Heterogeneous Surfaces : Kinetics of (Crickmore & Wojciechowski) .Alcohol Solvents: Photochemistry of Michler's Ketone in Cyclohexane and (Brown &Porter). . . . . .Aliphatic Carboxyiic Acids in Benzeke as Studieh by Partition: Hidration and Dimerization ofsome (Fujii & Tanaka) .. . . .Alkali Metal and Ammonium Chlorides in Wafer and Urea Systems. dG, AH, A,!? of Transferfrom Water to Mixtures containing up to 40% Urea (Pointud & Juillard) .Halides in Dilute Aqueous Solution at 25°C: Conductance of Some (Pethybridge &Spiers). . . . . .Alkylammonium Ions in' the Zeo1ite:L: Ekhange of kansant &'Peeters)Alkyloxy Radicals: Photolysis of Alkyloxy Vanadium (v) Chelates. A' Possible GeneralRoute to (Aliwi & Bamford) .Alloys : Thermodynamics of Hydrogen 'Dissolved in Pailadi&/Rhodi& and Palladium;Platinum (Clewley, Lynch & Flanagan)under Conditions of Constant Volume: Thermodynamic Properties of Hydroien inPalladium and its (Oates & Flanagan) .. . .7-AI2O3 : 1.r. Spectroscopic Study of COz Adsorption ontb (Morterra, Zecchina, Coluccia &Chiorino) . . . . . . . . . . . .y-Alumina. Part i.-Development of Sites Active in Energy Transfer: y-Radiolysis of MethaneAdsorbed on (Norfolk & Swan). .Aluminium (m), Gallium (n~) and Indium (mi: Enthalpies of 'Combustion of Tris-(Acetyi-acetonato) Derivatives (Cave11 & Pilcher) . . . .Amines: Interaction of Duraquinone Lowest Triplet with iAmo;yal & Bensasson)Amphoteric Latex Colloids: Heterocoagulation of (James, Homola & Healy) . . .E.S.R. Study of Ion Pairs Involving the Pyrene (Claridge & Kirk) .in various Pure Solvents and Binary Aqueous Mixtures : Solvation Spectra.Part 53.-Infraredand Nuclear Magnetic Resonance Studies of the Tetrahydroborate (Straws, Symons &Annealing Temperature on Dissolution Kinetics of Nickel Oxide : Semiconducting Oxides.9, 10-Anthraquinone-2-sodium sulphonate in Aqueous Solution. Part 3.-Pulse and GammaRadiolysis: Photochemistry and Radiation Chemistry of (Clark & Stonehill)Aqueous and Nonaqueous Solvents: Solubility of Nitric Oxide in (Shaw & Vosper)Solution at 25°C: Conductance of Some Alkali Metal Halides in Dilute (Pethybridge dSolution at Elevated Temperatures. The Effe'ct of Temperature on the Ioni'sation Cons'tant of .Solution Part 3.--w-hino acids and related compounds : Apparent Molal Heat Capacitiesof Organic Compounds in (Cabani, Conti, Matteoli & Tani)Solution Part 3.-Pulse and Gamma Radiolysis: Photochemistry a d Radiation Chemistryof 9,1O-Anthraquinone-2-sodium sulphonate in (Clark & Stonehill) .. . .Solutions : Homogeneous Catalysis of Cathodic Reduction of Oxygen in Copper-Cystamine(Bettelheim, Faraggi, Hodara & Manassen) . . . . . . .Solutions of Group IIB Metal Salts at 298.15 K. Part i.-Isothermal Transport Propertiesof Cadmium Iodide: Transport in (Paterson, Anderson & Anderson) .Solutions of Group IIB Metal Salts at 298.15 K. Part 2.-Interpretation and Predickon o'fTransport in Dilute Solutions of Cadmium Iodide: An Irreversible ThermodynamicAnalysis : Transport in (Paterson, Anderson, Anderson & Lutfullah) . . . .Arene Chromium Tricarbonyls and Photoinitiation of Polymerization : Photolysis of (Barn ford,59SUBJECT INDEX-VOLUME 73, 1977 5Association: Interpretation of the Thermodynamic, Spectroscopic and Dielectric Properties ofAtoms with Methyl and Ethyl Nitrates: Reaction of Oxygen (Salter & Thrush) .. . . .Azoisopropane: Comparison of the Mechanisms of the Thermal Decompositions of 2,2'-Solutions of Ethanol in Cyclohexane in Terms of (Stokes) . . . . .with Nitromethane and with Nitroethane: Reaction of Oxygen (Salter & Thrush)Azoisobutane and (McKay, Turner & Zarb) . . . . . . . .BBelousov-Zhabotinskii Oscillating Reaction to Addition of either Bromide or Cerium (IV) Ions :Reaction: Analysis of the Dependence on Temperature of the Frequency of Oscillation ofBenzoylferrocene in Hydroxylic Solvents : Photo-effects on (Heaney, Logan '& Powell) .Beryllium Sulphate Solution at High Pressure: Conductance of (Hsieh, Ang & Chang) .Bidimensional Phase Change in the Monolayer of Nitrogen or Argon Adsorbed on Graphiteat 77 K: Calorimetric Evidence for a (Rouquerol, Partyka & Rouquerol)Binary n-Alkane Mixtures: Prediction of Infinite Dilution Activity Coefficients in (Laud,Martire & Purnell) .. .Binding-induced Conformational Transition * of Sodium Poi;-L-Giutamate by Iron (In\Complex Ions in Aqueous Solution (Branca & Pispisa)to Poly(a-L-lysine HBr) from Polar Solvent Mixtures: Preferential (Komiyama, Mori,Yamamoto & Iijima) . . . .Binuclear Bridging Complexes of' Sulphate Adsorbed on Geothite (cc-FeOOH) : InfraredSpectra from (Pafitt & Smart)Biological Interest: Absorption Spectra of Radical Ions' of Polyenks of '(Lafferty, Roach,Sinclair, Truscott & Land) .. . .Biomolecules : Experimental and Theorehcal Aspects of Hydraiion Is0 therms for (Gascoyne& Pethig) . . . .Bromide Ion: Far-Ultraviolet' Solution Spectrbscopy of the (Fox & Hayon)or Cerium (IV) Ions : Response of the Belousov-Zhabotinskii Oscillating Reaction to' Add;-tion of either (Blandamer & Roberts) . . . . . . . . ,Response of the (Blandamer & Roberts) . . . . .the Frequency of Oscillation of the (Blandamer & Roberts) . .Calcium Sulphate/Water. Part 5.-Surface Area and Porosity Changes in the Dehydration ofCalculation of Rate Constant and Activation Energy : Kinetics of Electron Transfer Reaction .Calorimetric Evidence for a Bidimensional Phase Change in the Monolayer of Nitrogen orPart 1.-Alkali and Alkaline Earth Metal Forms: Water in Homoionic andCapillary Method for Tracer Diffusion Measurements in Liquids : Ciosed '(Passiniemi,Phenomena : Part 5.-Equilibrium and Stability of Soiid Cones in Fluid/Fluid Interfa&Carbon Monoxide in Molten'Carbonates'.Confirmation o f the Exisience of the Cot- Ion:Kinetics and Mechanism of Electrochemical Oxidation of (Borucka & Appleby) .Carbonylation of Monohydric Alcohols : Selectivity of a Heterogeneous Rhodium Catalys;Carbonyls: Activities of Olefinic Derivatives as Components of Photohi tiat'ing Systems basedon Transition-Metal (Bamford & Mullik)C-14 as Tracer: Slow Gas-Phase Oxidation of Ethylal with iMolek, Garcia-Domkguez;Rodriguez-Lbpez & Santiuste) ..Catalysis in Solution. Part 15.-Theoretical' Treatment ' of Parallel Firsi-Ordir Catalysedand Uncatalysed Reactions : Heterogeneous (Spiro) .with Elimination Reactions as an Example : X-ray Pho;oelec&on Spectroscopy andHeterogeneous (Vinek, Noller, Ebel & Schwartz)Catalyst in a Static System: Hydrogenation of Acetylene in Excess Ethylene on an AiuminaSupported Palladium (McGown, Kemball, Whan & Scurrell)Lattice : Chemiluminescence during Catalysis. Part 2.-Luminescent Transitions of someRare-earth Activators Embedded in the (Aras, Breysse, Claude], Faure & Guenin) .Catalysts: Effect of Ethylene and Hydrogen Adsorption on the E.S.R.Spectra of Chromia-Catalytic Activity Measurements : Acidic Properties of Silica-Alumina Gels as' a FunctionActivity of Co,Mgl - ,A1204 Spinel Solid Solutions, Part 1 .-Cation Distribut'ion of Co2;Calcium Sulphate Dihydrate: Studies in the System (Ball & Norwood) .between Manganate and Permanganate Ions (Dolin, Dogonadze & German)Argon Adsorbed on Graphite at 77 K (Rouquerol, Partyka & Rouquerol) .Heteroionic Mordenites : A (Coughlan, Carroll & McCann).Study.Liukkonen & Noszticzius) . . .(Boucher & Kent). . .for the (Christensen & Scurrell) . . . ..Alumina (Ashmawy & Steiner) . . . .of Chemical Composition. Titration and (Damon, Delmon & Bonnier)Ions: Structure and (Angeletti, Pepe & Porta) 6 SUBJECT INDEX-VOLUME 73, 1977Activity of Iron Oxide and Magnesium Oxide Solid Solutions.Part 3.-E.S.R. Characteri-sation: Structure and (Cordischi, Pep, Schiavello & Valigi)Oxidation of Furan to Maleic Anhydride: Similarity in the Reactivity of 0; and DoubleBond Type Lattice Oxygen as revealed by Vapour-Phase (Akimoto & Echigoya) . .Cathodic Reduction of Oxygen in Copper-Cystamine Aqueous Solutions : HomogeneousCations: a Radiation and Electron Spin Resonance Study: Solvation Spectra. Part 52.-The Aquation of Silver Atoms and (Brown & Symons)Cerium (IV) Ions: Response of the Belousov-Zhabotinskii Oscillating Reaction to'Addiiion o ieither Bromide or (Blandamer & Roberts)Charge Density Effects in Ion Exchange.Part 1 .-Heterovalen't Exchange Equilibria(Maes & Cremers) . . .Charge Transfer Interaction between Thiols aiid Aniines : Hydrogen Bonding Type (Yamabe,Akagi, Hashimoto, Nagata & Fukui)Spectra and Ionization Potentials of the Donois : Molecular Complexes of SubskutedAryl Diphenylmethyl Sulphides with n-Acceptors (Reichenbach, Santini & Aloisi) .Chemi-ionisation: Molecular Beam Study of Surface (Normington, Bomse & Grice) .Chemiluminescence during Catalysis. Part 2.-Luminescent Transitions in some Rare-earthActivators Embedded in the Catalyst Lattice (Aras, Breysse, Claudel, F a r e & Guenin).Chemisorbed on Raney Nickel Studied by Neutron Inelastic Spectroscopy : Different Speciesof Hydrogen (Renouprez, Fouilloux, Coudurier, Tocchet ti & Stockmeyer) .Chemisorption.Part 2.-Theoretical Models : Kinetics of Activated (Aharoni & Ungarish)Part 3.-Amount and Distribution of Adsorbate at Varying Temperatures and Pressures :Chromate: Photoinduced Oxidation of Propan-2-01 by Acid (Kianing)Chromatography: Temperature Dependence of the Interaction Second Viriai Coefficien; using.Chromia-Alumina Catalysts : Effect of Ethylene and Hydrogen Adsorption on' the E.S.R.Dehydrogenation Catalysts : Heterogeneous Structures in Promo-ted (Masson, Bonnier;Chromium Tricarbonyls and Photoinitiation of Polymeriza~ion : Photo1 ysis of Arene (Barn ford;C1(2P) with Molecular Hydrogen from' 200-500 K': Absolute' Rate of Reaction of (Lee;COz Adsorption onto 7-AIzO3 : 1.r.Spectroscopic Study 0.f (Morterra, Zecchina,' Coluccia &Cob(1)alamin with Nitrous Oxide 'and Cob(~rr)alamin: Reaction of (Blackburn, Kiaw &Swallow) .Cobalt Acetylacetonates : Decompdsition of l-Phenylethyl Hydioperoxide in the' Presence of(Vasvari & Gal) . .Oxidation of l-Phenyiethanol in ;he Presence of (Vasvhri & Gal)-60 y-Ray Induced Oxidation of Ferrous Sulphate Solutions : Effect of Sulphuric Acid(Matthews) .Colloids: Heterocoagulation of Amphotekc Latex (James,' Hornola & Heal;)Combustion of Tris-(Acetylacetonato) Derivatives of Aluminium (111), Gallium (111 )'and Indiun;(111): Enthalpies of (Cave11 & Pilcher) .Compaction on the Surface Area and Porosity of Six Powders by Measurement bf NitrogenSorption Isotherms: Study of the Effect of (Gregg & Langford) .Cornpartmentalised Free-Radical Polymerisation Reactions.Part 1 : Theory of (Biriwistle& Blackley) .Complexes between Pyridine and Phenol in Carbon Tetrachloride' Solutions : Hydrogen-bonded(Beezer, Hawksworth, Orban & Tyrrell) .of Trifluoroacetic Acid with Hexaoxa-"Crown" Ethers': Conductometric Investigaiion of(Nae & Jagur-Grodzinski) .Part 1 .-The Reduction of Oxygen in'the Co(1r) <A&onia 'Systems: Eiectro;educ;ion ofCobalt-Amino Peroxo (Bettelheim, Faraggi, Hodara & Manassen)Part 2.-The reduction of Oxygen in the Co(rr)-Ethylenediamine and Co(~~)iTriethylene:tetramine Systems : Electroreduction of Cobalt-Amino Peroxo (Bettelheim, Faraggi,Hodara & Manassen)Concentration Dependence o'f the' Flory-Huggins Parameter * into ' the Theory o f .StericStabilization: Perturbation Method for Incorporating the (Evans & Napper) .Conductance of Beryllium Sulphate Solution at High Pressure (Hsieh, Ang & Chang) .of Some Alkali Metal Halides in Dilute Aqueous Solution at 25°C (Pethybridge &Spiers). . . . . . . .Conductivity in Copper Formate Tetrahidrate 1 Protbnic (Murphy &'Flanagan) .of (n-butyl),Nd (n-butyl),B- as a Function of Temperature and Pressure : Molar (Speedy)Conductometric Investigation of Complexes of Trifluoroacetic Acid with Hexaoxa-"Crown"Catalysis of (Bettelheim, Faraggi, Hodara & Manassen) . . . .SUBJECT INDEX-VOLUME 73, 1977Cones in Fluid/Fluid Interfaces : Capillary Phenomena.Part 5.-Equilibrium and StabilityConstant Volume : Thermodynamic Properties of Hydrogen in Palladium and its Alloys unde;conditions of (Oates & Flanagan)Coordination Equilibria in Three-Component Systerrk of the Type MBr, + h i d i n e + Chloro:benzene (M = Zn, Co, Ni, Cu and Zn): Phase and (Libui & Kluczkowski).Copper Containing Spinel Solid Solutions (Cu,Mg, - &l1204): Solid State Properties of(Sharpe & Vickerman) . :Corrosion at Silver Electrodes. A Raman Spectroscopic Study : Thiocyanate Adsorption andCo-solvent Mixtures: Influence of the Solvent on the Rates of SNl-Type Solvolysis Reactionsof Metal Complexes in Water+ (Wells) .“Crown” Ethers: Conductometric Investigation of Complexes ‘of T&luoroacetic Acid withHexaoxa- (Nae & Jagur-Grodzinski) .. .Crystalline Hexamethyldisilane : Diffusion in (Salthduse & SheiwoodjPhotophysical Ekhaviour : Acridine: An Investigation of its Molecular and ( W i l l i d &Clarke) . .Cull Exchanged Y:Type’Zeolite : Determination of the Act‘ive Siie and Mechanism for Alkeneof Solid (Boucher & Kent) . . . ..:Electron Spectroscopic Study of Nitrogen Species Adsorbed ‘on (Matloob & koberls)Formate Tetrahydrate: Protonic Conductivity in (Murphy & Flanagan) . .(Cooney, Reid, Fleischmann & Hendra) . . . . ..Isomerization in (John & Leach) . . . . . . . . . .DDecomposition and Reduction of “Nickel Peroxide” by Thermal Analysis : Investigation ofof 2,Y-Azoisobutane and Azoisopropane : Comparison of the Mechanisms of the Thermalof 1,2-Epoxypropane: Kinetics of the Thermal Gas-Phase (Fiowersj ..of 1-Phenylethyl Hydroperoxide in the Presence of Cobalt Acetylacetonates (Vasv6ri & Gal)of 1,3,5-Trinitrohexahydro-l,3,5-triazine (RDX) : Mass Spectrometric Study of the Thermalof Zinc Nitrate Hexahydrate: E.S.R. Investi’gation of the Thermal (Campbell) *Dehydration of Calcium Sulphate Dihydrate : Studies in the System Calcium Sulphatel Water. .Dehydrogenation Catalysts: Heterogeneous Structures in Promoted Chromia+AluminaDesorption of Electrolytes at Liquid-Vapour and Liquid-Liquid Inteifaces ‘(Aveyard, SaIeemWork and Entropy of Adhesion’at Liquid-Liquid Inteifaces ’and ;he Relationship to Sal’tDiatomic Free Radicals Using Mass Spectromktry. ’ Part 4.-The Br; OCiO and BrO’+ClOMolecules with Clean Metal Wire Surfaces. Part 1 .-Hydrogen on Tungsten: Interactionof (Couper & John)Molecules with Clean Metal Wirk Surfaces.Part 2.Nitrogen on Tungstkn: Ikeracfion of(Couper &John) . . .Properties of Solutions of Ethanol in Cyclohexane in Terms of Association: Interpretationof theThermodynamic, Spectroscopicand(Stokes) . . . . . . .Spectra of Synthetic Zeolites X: Interpretation of the “Intermediate Frequency” (Ravalitera,Carru & Chapoton)Diffraction Data of Aqueous Electrolyte Solutibns : Termiiation’Errois in Fourie; Anaiysis ofDiffusion-controlled : Arrhenius AcGvation Energy of Readtions ;hat are almost (Logad) : Triplet Energy Transfer in 2-Methylpentan-2,4-diol: Viscosity Dependence of (Dainton,Henry, Pilling & Spencer) .Diffusion Enthalpies and Entropies in Thekally Forming NiO and (Ni;Fe)O from SO&1200°C (Tomlinson) ..for Iodine in Mixed Solven’ts: Activation Enthalpy of &&anishi & Nishimoto) .in Crystalline Hexamethyldisilane (Salthouse & Sherwood) . . .Measurements in Liquids : Closed Capillary Method for Tracer (Passiniemi, Liukkonen &Noszticzius) . . . . . . . . .Diffusivities Obtained fiom Nuclear Magnetic Resonance and Sorption Experiments : Inter-pretation and Correlation of Zeolitic (Karger & Caro) . . . . . . .3,4Dihydroxytoluene: Pulse Radiolysis of (Gohn & Getoff) . .Dimerization of Some Aliphatic Carboxylic Acids in Benzene as Studied by Parktion.Hydration and (Fujii & Tanaka) .. . . . . . . . .the (Bond & Tripathi) * . . . . .(McKay, Turner & ZarC) . . . . . . .(Bradley, Butler, Capey & Gilbert) .Part 5.-Surface Area and Porosity Changes in the (Ball & Norwood).(Masson, Bonnier, Duvigneaud & Delmon) . . . .& Heselden) .(Aveyard & Saleem) .Reactions: Kinetic Studies of (Clyne & Watson) . . . . . .Dielectric Properties of Hydrated Protein’s at 9:9 GI& (Bo’ne, GascoGe & Pethig) .(Triolo & Ruffo)8 SUBJECT INDEX-VOLUME 73, 1977Dispersions. Part 1 .-Identification of Parameters in Structural Hysteresis : Mechanics ofDissociation of 2-Methilbut-i -ene and the Resonance Energy o f the 2-Mkthylallyl RadicaiDissolution and Passivation of Nickei.An X-;ay Photoeiectron Spkctroscopy * Stud;Kinetics of Nickel Oxide : Semiconductkg Oiides.. The'Effect of Prior Annealing Tempera:(Spaull) . . .(Trenwith & Wrigley) .(Dickinson, Povey & Sherwood) + .ture on (Jones, Segall, Smart & Turner) .Duroquinone Lowest Triplet with Amines: Interaction of (Arnouyal & Bensasson)EElectrical Resistivity of Solutions of Nitride, Hydride and Deuteride : Solutions of LithiumSalts in Liquid Lithium. The (Adams, Down, Hubberstey & Pulham)Electric Discharge by an Electron Spin Resonance Spin Trapping Technique : Dktection andIdentification of Organic Radicals Produced in the Low Pressure Silent (Hibbert,Robertson & Perkins) .Field Calculations for the MonomerLDimir Shift and for Complexes 'with 'Fluoiide oEAcetate Anions: Proton Chemical Shifts of Hydrogen Bonded Complexes of Acetic Acid(Akitt) .. .Electrochemical Luniinescence of Rubrene Dissolved in Benzonitrile 'in Thin C&s (Dunnet't& Voinov) . . ,Oxidation of Carbon'Monoxide in Molten Carbonates. Confirmakon of the Existince ofthe COi- Ton: Kinetics and Mechanism of (Borucka & Appleby)Study: Gibbs Energy of Formation of SO,. A High Temperature (Rosenqvist '& WahgomjElectrode Forcing Functions : Ring-Disc Electrodes. Part 17.-Ring Response to PeriodicDisc (Bruckenstein, Tokuda & Albery)in the Acetonitrile+Ethylene Glycol Solvent System 'at 25°C: Studies in IsodielectricSolvents. Part 1 .-Standard Potentials of the Silver-Silver (Bose & Kundu)Part 8.-Oxygen Evolution at Ruthenium Dioxide Anodes : The Oxygen (Burke, Murph;,Electrodes: Spectral Distributions of Photo-eiectrodhemical Reactions over Meial Phthalo:Electrolytes at Liquid-Vapour and Liquid-Liquid Interfaces : Deiorption ok (Aveyard;in Tetramethylurea: Physico-Chemical Studies in Nonaqueous Solvents.Part 13.-Electrolyte Solutions : Termination Errors in Fourier Analysis of Diffraction Data of AqueousViscosities in Hexamethyl'phosphotriamide at 25°C (Sacco; Petrella, Della' Monica &Electromotive Force Measurements : Ionic Product and Enihalp; of Ionization of'wate; fromElectronic Transference Numbers of Polymers Determination of (Peht & Jozefowicz):Electron Spectroscopic Study of Nitrogen Species Adsorbed on Copper (Matloob & RobertsjElectron Spin Resonance Spin Trapping Technique : Detection and Identification of OrganicRadicals Produced in the Low Pressure Silent Electric Discharge by an (Hibbert, Robertson& Perkins) .. . . . .Studies of Elementary Processes in Radiation- and Phoio-chemistry. Part 14.-Photolysisof Solutions Containing Maleimides (Ayscough, English, Lambert & Elliot) .Study of the 1 : 1 Hydrogen-Bonded Complex of Di-t-Butylnitroxide with Methanol. AnAnalysis of an Acceptor: Self-Associated Donor Equilibrium (Bullock & Howard) . .Study: Solvation Spectra. Part 52.-The Aquation of Silver Atoms and Cations : a Radiationand (Brown & Symons) .Electron Transfer and Electronic Excita'tion : 'Geneialised For; ter Cycle.* TheirnodynamicRelationships between Proton Transfer (Grabowski & Rubaszewska) .Calculation of Rate Constant andActivation Energy: Kinetics of (Doh, Dogonadze & German) . . .Electroreduction of Cobalt-Amino Peroxo Complexes. Part 1 .-The Reduction of Oxygeiin the Co(n)+Ammonia System (Bettelheim, Faraggi, Hodara & Manassen)of Cobalt-Amino Peroxo Complexes. Part 2.-The Reduction of Oxygen in the Co(rI):Ethyl:enediamine and Co(a)-Triethylenetetramine Systems (Bettelheim, Faraggi, Hodara &Elevated Temperatures. -The Effect 'of Temperature on the Ionisation Constant of the 2,2'Bipyridyl Cation: Spectrophotometric Investigations in Aqueous Solution at (BuissonElimination Reactions as an Example : X-ray Photoelectron Spectroscopy and HeterogeneousCatalysis, with (Vinek, Noller, Ebel & Schwartz)Elovich Equation for the Kinetics of Adsorption of Gases on Solids: Aliernatjve to ;he (Ritchiej..O'Neill & Venkatesan) .. .cyanine (Meshitsuka & Tamaru) .Saleem & Heselden) . . . . . . .Thermochemical Studies of some 1 : 1 (Paul, Jauhar, Banait & Narula) .(Triolo & Ruffo) . . .Castagnolo) . . . . .(Covington, Ferra & Robinson). .Reaction between Manganate and Permanganate Ions.Manassen) . . . . . . . . . . .& Irving) . . . . . . .SUBJECT INDEX-VOLUME 73, 1977 9PAGEEmission and Absorption Characteristics of 2,3-Dicyano-p-hydroquinone: Effect of pH on the(Brown &Porter) . . . . .Studies of Solubilization in Micelles. Part 4.dtudies on Cationic Micelles' with 'addedElectrolyte and on Lecithin Vesicles: Excimer Formation and the Ham Effect: Absorptionand (Dorrance & Hunter) .. . . . .Emulsion Polymerization Kinetics : General Solution to the 'Smith-Ewart Equations for(Hawkett, Napper & Gilbert) . . . . . . . . .Energetically Heterogeneous Surfaces : Kinetics of Adsorption on (Crickmore & Wojcie:chowski) . . . . .Energy Separation between Triplet and Single; Meihylene : Kinetics of Methyleie Additionto cis- and trans-But-2-ene (Frey & Kennedy) . . . . . . .Energy Transfer in 2-Methylpentan-2,4-diol: Viscosity Dependence of Diffusion-controlledTriplet (Dainton, Henry, Pilling & Spencer) . . . .: y-Radiolysis of Methane Adsorbed on 7-Alumina. Part 1 .-Development of Sites Activein (Norfolk & Swan) .. .Enthalpies and Entropies in Thermally Forming NiO and (Ni, Fe)O from 800-1200°C':Diffusion (Tomlinson) .and Entropies of Ionization of 2-'and 3'- Substituteh Phenols in Met'hanof+ Water Mixtures(Rochester & Wilson) . .of Combustion of Tris-(Acetylacetonato) Derivat kes of AlAinium (HI),' Gallium (k) andIndium (m) (Cave11 & Pilcher)of Mixing: Thermodynamic Functions' for the System Ethanol + Ciclohexane from Vapou;Pressures and (Stokes & Adamson).of some Binary Mixtures of 1,2-Dichloroethane andHydrocarbons : Excess iMahi & Khurma)of Transfer for KBr, KI, HBr and HI: Solute-Solvent Interaction in Water+t-ButylalcoholMixtures. Part 9.- (Pointud & Juillard) ..Enthalpy of Diffusion for Iodine in Mixed Solvents :'Activation '(Nakanishi' & Nkhimoto)of Ionization of Water from Electromotive Force Measurements : Ionic Product and(Covington, Ferra & Robinson)Entrainment Method: Thermodynamic Study' of the Chemical Vapour Transport SystemGaAs-HBr Using a Modified (Faktor, Garrett, Lyons & Moss) .Entropies of Hydrobromic Acid in Ethanol+ Water Mixtures : Structure of Aquo-aldoholicsolvents: Transfer Free Energies and (Das, Bose & Kundu)Entropy of Adhesion at Liquid-Liquid Interfaces and the Relationship to' Salt Desoipt ion:Workand (Aveyard & Saleem) . . . .1,ZEpoxypropane : Kinetics of the Thermal Gas-Phase Decomposition of (Floweis)Equilibrium and Stability of Solid Cones in Fluid/Fluid Interfaces : Capillary Phenomena:Part 5.- (Boucher & Kent) .. . . .Concentrations: Numerical Estimation' of (Daul & Gobi)E.S.R. Characterization: Structure and Catalytic Activity of Iron Oxide and Magnesium' OxideSolid Solutions. Part 3.- (Cordischi, Pepe, Schiavello & Valigi)Investigation of the Thermal Decomposition of Zinc Nitrate Hexahydraie (Campbeli)*Measurements : Interaction of Di-t-Butyl Nitroxide with Alkanols : (Atherton, Manterfield',Oral & Zorlu)Spectra of Chromia-Alumina Catalyst's : Effect of Ethilene and Hidrogen Adsorption onthe (Ashmawy & Steiner) . . .Study of Ion Pairs Involving the'perylene Anion (Claridge &.KirkjStudy of Ion Pairs Involving the Pyrene Anion (Claridge & Kirk) .Ethanol + Cyclohexane from Vapour Pressures and Enthalpies of Mixing :.Thermodynamic+Water Mixtures: Structure of Aquo-alcoholic solvents : 'Transfer Free Energies andFar-Ultraviolet Solution Spectroscopy of the Bromide Ion (Fox & Hayon) . . . . 872Solution Spectroscopy of the Iodide Ion (Fox & Hayon) . . 1003Fast Reactions in Non-Aqueous Solvents : Application of the Pressure:Jump Technique' to theMeasurement of Rates of (Buschmann, Knoche, Day & Robinson) . . , . 6710 SUBJECT INDEX-VOLUME 73, 1977Ferrous Sulphate Solutions: Effect of Sulphuric Acid on the Cobalt-60 y-Ray Induced Oxida-tion of (Matthews).Films in the Oxidation of Oxala'te Ion : Photoel&trocatalysis by' Metal PhihalocyaninkEvaporated (Meshitsuka & Tamaru) .Flash Photolysis of Ketene.Photolysis Mechanism and Rate Constants for Singlet and TripletMethylene (Pilling & Robertson) .Flory-Huggins Parameter into the Theory of Steric' Stabkzation : Perturbation 'Method fo;Incorporating the Concentration Dependence of the (Evans & Napper)Flow System: Studies of the Kinetics of Nucleation and Growth of Pigment Dispersions Using aLaser Light-Scattering Apparatus in a (Nobbs & Patterson)Fluid Interfaces: Capillary Phenomena. Part 5.-Equilibrium and Siabilit; of Solid 'Conesin Fluid/ (Boucher & Kent) .Fluorescence in Inverse Micelles : Quenching of Pyrene Sulphonate (Miller, Klein & Hauser)Forster Cycle. Thermodynamic and Extrathermodynamic Relationships Between ProtonTransfer, Electron Transfer and Electronic Excitation : Generalised (Grabowski &Rubaszewska) .Fourier Analysis of Diffraction Data of Aqueous Electroiyte Solutions : Terminkon 'Errors(Triolo & Ruffo) .Free Energy of Transfer of Ionic Surfact'ants from Water 'to Water+Acetone Mixtures fromVapour Pressure Measurements : Standard (Treiner & Le Besnerais)Part 1 : Theory of Compartmentalised (Birtwi'stle &Blackley) .Part 4.-The Br$ OClO and BrO'+ClO Reactions':Kinetic Studies of Diatomic (Clyne &Watson) .Frequency" Dielectric Spectra of Synthetic Zeolites X: Interpretation of ;he "Intermediate(Ravalitera, Carru & Chapoton) .of Oscillation of the Belousov-Zhabotinskji Reaction': Analysis 'of the Dependence onTemperature of the (Blandamer & Roberts) .. .-Radical Polymerisation Reactions.Radicals Using Mass' Specirome;ry.GGaAs-HBr Using a Modified Entrainment Method : Thermodynamic Study of theChemical Vapour Transport System (Faktor, Garrett, Lyons & Moss)Gases on Solids: Alternative to the EIovich Equation for the Kinetics of Adsorpt'ion of(Ritchie) .Gas-Liquid Chromatography : Temperature Dependence' of the Inferacti'on Second ' VirialCoefficient using (Neogi & Kudchadker) . .Oxidation of Ethylal with C-14 as a Tracer: Slow (Molera, Garcia-Doniinguez, Rodriguez-L6pez & Santiuste)Gibbs Energy of Formation of SO2 .. A High Tempeiature' Electrochemical Study( Rosenqvis;& Haugom).Glasses: Luminescence Following Laser 'Excitation 'of Tiapped Electrons' in Mixed-SoluteAqueous (Nguyen & Walker) .Goethite (cc-FeOOH) : Infrared Spectra from' Bin;cIear Bridging Cornpiexes o f SulphateAdsorbed on (Parfitt & Smart) .. .-Phase Decomposition of 1 ,ZEpoxypropane : Kinetics of the Thermal (Flowers).HHeat Capacities of Organic Compounds in Aqueous Solution. Part 3.--w-Amino acids andrelated compounds : Apparent Molal (Cabani, Conti, Matteoli & Tani)Heats of Formation of the Silicon Subchlorides SiCl(g), SiCl,(g) and SiCl,(g): Mass Spectro:metric Determination of the (Farber & Srivastava)Heterocoagulation of Amphoteric Latex Colloids (James, Homoia & Heal y jHeterogeneity of Solid Particulates using the Patchwise Adsorption Model : Determination ofthe Surface (House & Jaycock)Heterogeneous Acid-base Catalysis.Part 1 .-Cataiysis of the' Hydiolysi; of AcetaldehydeDimethyl Acetal (1,l-Dimethoxyethane) by Methacrylic Acid-divinylbenzene Copolymer(a weak-acid ion-exchange resin), and the Characterisation of Polymer Catalysts (Gold& Liddiard) . . . . .Acid-base Catalysis. Part 2.-Catalysis of the. Hydrolysis'of Ethyl Vinyl Ether (ethoxyethenc)by Methacrylic Acid-divinylbenzene Copolymer Weak-acid Ion Exchange Resins (Gold,Liddiard & Martin) . . .Catalysis in Solution. Part 15.LTheoretical Treatment of Parallel Firs't-Order Catalysedand Uncatalysed Reactions (Spiro) . . .Catalysis, with Elimination Reactions as an Example : X-ray Photoelectron Spectroscopyand (Vinek, Noller, Ebel & Schwartz) ., . . . . . . .SUBJECT INDEX-VOLUME 73, 1977 11Recombination of Atoms. Theory of the Smith-Linnett Method (Jablohski) .Rhodium Catalyst for the Carbonylation of Monohydric Alcohols: Selectivity of a(Christensen & Scurrell). . . . .Structures in Promoted Chromia+ Alumina Dehydrogenation Catalysts (Masson, Bonnier,Duvigneaud & Delmon) . . .Surfaces : Kinetics of Adsorption on Energeticall; (Cric*hore & Wojciechowski) . .Heterovalent Exchange Equilibria: Charge Density Effects in Ion Exchange. Part 1 .-(Maes & Cremers) . . . . .Hexamethylphosphotriamide a; 25°C : Elktrolyte Viscosities in (Sacco, Petrella, Della Monica& Castagnolo) . . .High Energy Reaction Pathways for Chemically Activated Insertion' Products : 'Reaciion ofSinglet Methylene with Methylenecyclopropane.Part 2.- (Clements, Frey & Walsh) .Temperature Electrochemical Study: Gibbs Energy of Formation of S02. A (Rosenqvist&Haugom) . . , . . . . .Homogeneous Catalysis of Cathodic Reduction of Oxygen in 'Copper-C;stamke AqueousSolutions (Bettelheim, Faraggi, Hodara & Manassen)Homoionic and Heteroionic Mordenites : A Calorimetric Study. Part 1 .-Alkali and Aikalin;Earth Metal Forms : Water in (Coughlan, Carroll & McCann)Hz180 Water (0 to 170°C): Vapour Pressure of Ice (-50 to 0°C) and (Jakli & StaschewskijHydrated Proteins at 9.9 GHz: Dielectric Properties of (Bone, Gascoyne & Pethig)Hydration and Dimerization of Some Aliphatic Carboxylic Acids in Benzene as Studied byIsotherms for Biomolecules : Experimental and Theoreti&il Aspects of (GascoGe & Pethig)Hydrocracking of n-Pentane (3-C13) with Type Y Zeolite : Hydroisomerization and (WeeksHydrogen Adsorption on the E.S.R.Spect;a of Chromia-Aiurnina Catalysts :'Effect of EihyleneHydrogenation of Acetylene in Excess Ethylene on an Alumi'na Supported Paliadium Catalyst inHydrogen Atoms with Ethane: Mass Spectrometric Study of the Reaction of (Jones, Morgan-bonded Complexes between Pyridine and Phenol in Carbon Tetrachloride Soiutions(Beezer, Hawksworth, Orban & Tyrrell) .Bonded Complexes of Acetic Acid.Electric Fieid Caiculati'ons for the' Monomer-Dime;Shift and for Complexes with Fluoride or Acetate Anions: Proton Chemical Shifts of (Akitt)Bonded Complex of Di-t-Butylnitroxide with Methanol.An Analysis of an Acceptor:Self-Associated Donor Equilibrium: Electron Spin Resonance Study of the 1 : 1 (Bullock&Howard) .-bonding Reactions : Note 'on the Proton-Donating Ability of Water in (Christian, Tuckei& Mitra)Bonding Type Charge Transfer Interaction between Thiols and Amines '(Yamabe, Akagi,Hashimoto, Nagata & Fukui).Dissolved in Palladium/Rhodium and Paliadium/Platinum 'Alloys : Thermodynamics of(Clewley, Lynch & Flanagan) . . .in Metals: Application to Pd/H(D): Isotope Effec; for ;he Soiution'of (Oates & Flanagan)in Palladium and its Alloys under Conditions of Constant Volume: ThermodynamicProperties of (Oates & Flanagan) . . . . .on Tungsten: Interaction of Diatomic Moiecule; with Clean Meial Surfaces.Part 1.-(Couper &John) . . . .Yield in Some Radiation Chemical SGstems: Reactions' of Hidrogen Atoms and AliphaticRadicals with Monovalent Cadmium and Nickel Ions as a Source of (Freiberg &Meyerstein) .Hydroisomerization and Hydiocracking hf n-Pentane (3-d' 3, with Type Y 'Zeoliie (Weeks &Bolton) .Hydrophobic Interaction: Solute Interactions' in Dilute 'Solutions. * Part' 2.-A StaiisticaiMechanical Study of the (Clark, Franks, Pedley & Reid) . . . . .Interaction : Solute Interactions in Dilute Aqueous Solutions. Part 3.-Volume ChangesAssociated with the (Franks) . . . . .Hydroxylic Solvents: Photo-effects on Benzoylfkrro&ne in iHeaney, Logan & Powell) .Hysteresis: Mechanics of Dispersions.Part 1 .-Identification of Parameters in Structural(Spaull)Isotope Exchange Reactions. Part 3.-HzSi-D2 (Pratt & Rogers)Partition (Fujii & Tanaka) . .& Bolton)and (Ashmawy & Steiner) . . . . .a Static System (McGown, Kemball, Whan & Scurrell) . . .& Purnell) . . .Ice (-50 to OOC) and Hzl*O Water (0 to 170°C): Vapour Pressure of H2'*0 (Jakli &Staschewski) . . . 1505in Porous Solids: Meiting of (Rennie & Clifford) ' : . . . . 6812 SUBJECT INDEX-VOLUME 73, 1977Infinite Dilution Activity Coefficients in Binary n-Alkane Mixtures : Prediction of (Laub,Infrared and Nuclear Magnetic Resonance Studies o i the Tetrahydroborate. Anion in variousPure Solvents and Binary Aqueous Mixtures: Solvation Spectra.Part 53.- (Strauss,Symons & Thompson)Approach: Evolution of the Acidic Properiies 0; Silica-Alumina'Gels 'as a Funciion 0.fChemical Composition (Scokart, Declerck, Sempels & Rouxhet) .Spectra from Binuclear Bridging Complexes of Sulphate Adsorbed on Goethite'(or-FeOOHj(Parfitt & Smart) . . . .Spectroscopic Study of the'Solvation of Ions in Methanol: Solvation Spectra. Part 5 4 . 1A Low Temperature (Strauss & Symons) .Spectrum of DNA(Na) in the Dry Solid State: Reversibie Temperature Dependent SpectraiShift in the (Rossiter) . . . . .Study of Effects of Sulphur-poisoning on the Adsorption of Carbon Monoxide by NickejStudy of the Adsorption of ['H,]Aceti'c Acid on tb Ruthe (Giiffiths & Rochester) :Study of the Adsorption of Hexafluoroacetone on to Rutile (Griffiths & Rochester) .Study of the Adsorption of Sulphur Compounds on Silica and Silica-supported NickeiStudy of the Adsorption of Watkr on'to the Surface of Rutiie (Ghffiths'and Rochester) *Study of the Surface of Silica Immersed in Liquid Mixtures of Hydrocarbons (Rochester1.r.Spectroscopic Study of CO, Adsorption onto ;-Al2O3 (Morterra, Zecchina; Coluccia &Insertion Products: Reaction of Singlet Methilene with Methyienecyclopropane. Pait 2 . iHigh Energy Reaction Pathways for Chemically Activated (Clements, Frey & Walsh) .Interaction of Di-t-Butyl Nitroxide with Alkanols : E.S.R. Measurements (Atherton, Manter-field, Oral & Zorlu) . .Interfaces: Desorption of Eledtroly ies at Liquid-Vapour and Liquid-Liquid'(Ave;ard, Saleemand Heselden) ..Iodide Ion: Far-Ultravihlet Solution Spedtroscopy of the (Fox & Haion)Ion Exchange. Part 1 .-Heterovalent Exchange Equilibria: Charge Density Effects in(Maes & Cremers) .Resins : Heterogeneous Acid-base Catalysis.. Par; 2.-Catal;sis of the Hydroiysis of EthjJ*lVinyl Ether (ethoxyethene) by Methacrylic Acid-divinylbenzene Copolymer Weak-acid(Gold, Liddiard & Martin) . . . .Ion Exchangers. Part 1 .-Quantitative Characterization and Thermodynamic Ba'sis : StabilityIonic Product and Enthalpy of Ionization of Water from Electromotive Force Measurements(Covington, Ferra & Robinson) .Ionisation Constant of the 2,2' Bipyridyl Cation : Spectrophotometric Investigations in AqueousSolution at Elevated Temperatures: The EA'ect of Temperature on the (Buisson & Irving)of 2- and 3-Substituted Phenols in Methanol+ Water Mixtures : Enthalpies and Entropies ofon Adsorption from Solution: Effects'of (Rendali & Smith) .Potentials of the Donors : Molecular Complexes of Substituted Aryi DiphenylmethyiCharge Transfer Spectra and (Reichenbach, Santini &Martire & Purnell) ....(Rochester & Terrell)(Rochester & Terreil)& Trebilco) . .Chiorino) . . .of Metal Uncharged Ligand Complexes in (Maes, Marynen & Cremers) . . .(Rochester & Wilson) . . . . .Sulphides with n-Acceptors.Aloisi) . . . . . . Ion Pairs Involving the Perylene Anion: E.S.R. Study of (Claridge &'Kirk)'Irreversible Thermodynamic Analysis : Transport in Aqueous Solutions of Group IIB MetalSalts at 298.15 K.Part 2.--Interpretation and Prediction of Transport in Dilute Solu-tions of Cadmium Iodide: An (Paterson, Anderson, Anderson & Lutfullah).Isodielectric Solvents. Part 1 .-Standard Potentials of the Silver-Silver Chloride Electrode inthe Acetonitrilef Ethylene Glycol Solvent System at 25°C: Studies in (Bose & Kundu).Isomerization in Cur1 Exchanged Y-Type Zeolite: Determination of the Active Site andMechanism for Alkene (John & Leach) .Isothermal Transport Properties of Cadmium Iodide : Tiansport in' Aqueous Solutions 0.fGroup IIB Metal Salts at 298.15 K. Part 1.- (Paterson, Anderson & Anderson) .Isotherms for Biomolecules : Experimental and Theoretical Aspects of Hydration (GascoyneInvolving the Pyrene Anion: E.S.R.Study of (Claridge & Kirk) . . ..& Pethig) .Isotope Effect for the Solution of 'Hydrogen in Metals: Application to Pd/H(D) (Oates &Flanagan) . . .Erect in Hydrogen Atom' Absiraction from Substitu'ted Phenols by Polyvinyl AcetateRadicals in Vinyl Acetate : Evidence for Tunnelling (Simonyi, Fitos, Kardos, Kovhcs,Lukovits & Pospi5il)SUBJECT INDEX-VOLUME 73, 1977 13PAGEKKetene. Photolysis Mechanism and Rate Constants for Singlet and Triplet Methylene :Kinetic and Thermodynamic Character of Reducing 'Speciks Produced on Pulse Radioiysis 0;Studies of Diatomic Free Radicals Using Mass Spectrometry. ' Part 4.-The Brk OCiO andKinetics: General Solution to the Smith-Ewart Equations for Emulsion Poiymerizationof Activated Chemisorption.Part 2.-Theoreti& Models (kharoni & Ungaiish) . .of Activated Chemisorption. Part 3.-Amount and Distribution of Adsorbate at Varyingof Methylene Addition to cis- and trans-But-2-ene. Further EGidence for the Energ;of the Chlorine-Photosensitized Oxidation of Hydrogen at 1 Atmosphere Pressure, '306 Kof the Hydrogen Reduction of Nickel Ions in Silica-Magnesia (Briend-Faure & DelafossejFlash Photolysis of (Pilling & Robertson).Acetonitrile (Bell, Rodgers & Burrows) , .BrO+C10 Reactions (Clyne &Watson) . . . . .(Hawkett, Napper & Gilbert) . . . . .Temperatures and Pressures (Aharoni & Ungarish) . . .Separation between Triplet and Singlet Methylene (Frey & Kennedy) .(Cox & Derwent) .. . . . ..LLanthanide Glycollate Systems: Potentiometric Studies of some (Carpenter, Monk & Whewell)Laponite: Adsorption and Oxidation of Dimethylaniline by (Vansant & Yariv) . . .Laser Excitation of Trapped Electrons in Mixed-Solute Aqueous Glasses : LuminescenceLight-Scattering Apparatus in a Flow System: Siudies of the Kinetics of Nucleation andLatex Colloids : Heterocoagulation of Amphoteric (James, Homola & Heaiy)Lattice Oxygen as revealed by Vapour-Phase Catalytic Oxidation of Furan to Maleic An:hydride: Similarity in the Reactivity of 0; and Double Bond Type (Akimoto & Echigoya)Lennard-Jones 12 : 6 Parameters for Ten Small Molecules (Clifford, Gray & Platts)Ligaod Complexes in Ion Exchangers.Part 1 .-Quantitative Characterization and Thermo-dynamic Basis: Stability of Metal Uncharged (Maes, Marynen & Cremers) .Liquid Crystal Phase Structure and Self-diffusion Coefficients in the System Lithium Perkuoro:octanoate+ water: Nuclear Magnetic Resonance Studies of (Tiddy)Liquid-Liquid Interfaces and the Relationship to Salt Desorption: Work and' Entrbpy ofAdhesion at (Aveyard & Saleem) .Lithium. The Electrical Resistivity of Sdlutions of 'Nitride, Hydride and DeuierideiSolutions of Lithium Salts in (Adams, Down, Hubberstey and Pulham)Mixtures of Carbon Tetrachloride, n-Octanol and Water at 20°C: Thermodynamics ofMixtures of Hydrocarbons: Infrared Siudy of the Surface of Silica Immersed in (RodhesteiMixtures of Methane and Ethene: Thermodynamics of kcalado & Soare;)Phase Hydrocarbon Oxidation.Part 4.-Hydroperoxide-Alcohol and Hydroperoxide-Ketone Transitions in the Oxidation of Ethylbenzene : Sequence Studies in (Danbczy,Nemes & Gd)-Vapour and Liquid-Liquid Interfaces : Deiorption of Electrolytes'at (Aveyard, Saleem &Heselden) . . .Liquids: Closed Method for 'Tracir Diffusion Measurements in (Passiniemi, Liukkonen &Noszticzius) . . . .Low Pressure Silent Electric Discharge by an Electrdn Spin Resonance Spin Trapping 'Tech:nique: Detection and Identification of Organic Radicals Produced in the (Hibbert,Robertson & Perkins) . . .Low Temperature Infrared Spectroscopic Study of the Solvation of Ions' in Methanol : SoivationSpectra. Part 54.-A (Strauss & Symons) .Luminescence Following Laser Excitation of Trapped Eiectrons in 'Mixed-Solute Aqueousof Rubrene Dissolved in Benzonitrile h Thin Cell's : Electrochemical (Dunnett '& Voinov)Following (Nguyen & Walker) .. . . .Growth of Pigment Dispersions Using (Nobbs & Patterson) * . . ..Miscible (Platford) . . .& Trebilco) . . . . 'Glasses (Nguyen & Walker) . .MMaleimides : Electron Spin Resonance Studies of Elementary Processes in Radiation- andPart 14.-Photolysis of Solutions Containing (Ayscough, English,Manganese Ions in Sodium Chloride Singie Cry&: Thermotransport'of (Willia.&s & Allnatt jPhotochemistry.Lambert & Elliot) . . .14 SUBJECT INDEX-VOLUME 73, 1977Mass Spectrometric Determination of the Heats of Formation of the Silicon SubchloridesStudy of the Reaction of Hydrogen Atoms with Ethane (Jones, Morgan & Puinell)Study of the Thermal Decomposition of 1,3,5-Trinitrohexahydro-l,3,5,-triazine (RDX)Spectrometry.Part 4.-The Br+ OClO and BiO + ClO Reactions : Kinetic Studies ofDiatomic Free Radicals Using (Clyne & Watson) , . .Mechanics of Dispersions. Part 1 .-Identification of Parameters in Structural Hysteresis(Spaull) .Mechanism of the Quaternization 'of Poly(4-iinyl pyridine) with Ethyl, n-PropyI, n:Butyi,n-Hexyl and Benzyl Bromide in Sulpholane : Kinetics and (Boucher, Groves, Mollett &Fletcher) . . . . . .Melting of Ice in Porous Solids (Rennie & Clifford) .Metal Complexes in WaterS-Co-solvent Mixtures: Influence of' the Solven; on fhe Rates ofSNl-Type Solvolysis Reactions of (Wells) .Metal Phthalocyanine Electrodes : Spectral Distributions of Photo-electrochemical Reactionsover (Meshitsuka & Tamaru) .IIB Metal Salts at 298.15 K.Part 1.-Isothermal Transport Pioperties of Cadmium Iodide:Transport in Aqueous Solutions of Group (Paterson, Anderson & Anderson)at 298.15 K. Part 2.-Interpretation and Prediction of Transport in Dilute Soluti'ons ofCadmium Iodide : An Irreversible Thermodynamic Analysis : Transport in Aqueous Solu-tions of Group (Paterson, Anderson, Anderson & Lutfullah)Metals: Application to Pd/H(D): Isotope Effect for the Solution of Hydiogen in (Oates kFlanagan)Metal Unchanged Ligand Complexes in Ion Exchan&rs. Part 1:-Quantitative Charadteriza:tion and Thermodynamic Basis: Stability of (Maes, Marynen & Cremers)Metal Wire Surfaces.Part 1 .-Hydrogen on Tungsten: Interaction of Diatomic MoleculesSurfaces. Part 2.-Nitrogen on Tungsien: Interaction of Diatomic Molecules with' Clean(Couper &John) .Metathetical Reactions. Pait 2.iAbstiaction of Chlorine Afoms by Cyclohekyl Rgdicalsfrom CHC12CN and CH2C1CN. Effect of Cyano-group Substitution on Rates of(Gonen, Horowitz & Rajbenbach) +Methanolic Solutions of Tetranitromethane: Pulse Radiolysis of: (Johnson & Salmon) :Methanol+ Water Mixtures : Enthalpies and Entropies of Ionization of 2- and 3-SubstitutedPhenols in (Rochester & Wilson)2-Methyl ally1 Radical : Dissociation of 2-Methylbui-1 -ene and ;he Resonance Energy 'of the3-Methyl-3-chlorodiazirine: Photolyk of '(Frey & Penny) 1Mica Surfaces: Comparison of Theory and Experiment : van der Waals Interaction betweenMicelles : Quenching of Pyrene Sulphonate Fluorescknce in Inverse (Miller,' Klein & HauserjPart 4.-Studies on Cationic Micelles with added Electrolyte and on Lecithin Vesicles :Excimer Formation and the Ham Effect: Absorption and Emission Studies of Solubiliza-tion in (Dorrance & Hunter) ..Michler's Ketone in Cyclohexane and Alcohol Solvents : Photochemisky of'(Bro\;n & Porte;)Miscible Liquid Mixtures of Carbon Tetrachloride, n-Octanol and Water at 20°C : Thermo-Mixtures: Enthalpies and Entropies' of Ionization of 2- and 3-substituted Phenols in MeihanoiPart 9.-Enthalpies of Transfer for KBr, KI, HBr and HI: Solute-Solvent Interaciion inof 1,2-DichIoroethane and Hydrocarbons : Excess Enihalpies of 'some Binary (Mahl &Molecular and Crystalline Photophysical Behaviour : Acridine: An Investigation of its(Williams & Clarke) .Beam Study of Surface Chemi-ionisation (Normington, Bomse & Grice) : 1Complexes of Substituted Aryl Diphenylmethyl Sulphides with n-Acceptors.ChargeTransfer and Ionization Potentials of the Donors (Reichenbach, Santini & Aloisi) .Hydrogen from 200-500 K: Absolute Rate of Reaction of C1(2P) with (Lee, Michael, Payne,Stref & Whytock) . . .Molecules : Lennard-Jones 12': 6 Parameters fok Ten'Smali (Clifford, Gray & Plaits)Molten Carbonates.Confirmation of the Existence of the C0;- Ion: Kinetics and Mechanismof Electrochemical Oxjdation in (Borucka & Appleby)Monolayer of Nitrogen or Argon Adsorbed on Graphite at 77 K: Calorimefric Eiidence for aBidimensional Phase Change in the (Rouquerol, Partyka & Rouquerol)Mordenites: A Calorimetric Study. Part 1 .-Alkali and Alkaline Earth Metal Forms:'WateEin Homoionic and Heteroionic (Coughlan, Carroll & McCann) . . . . .SiCl(g), SiC12(g) and SiCI3(g) (Farber & Srivastava) .(Bradley, Butler, Capey & Gilbert) . ,..with Clean (Couper &John) . . .(Trenwith & Wrigley) . . . .(Gregory 1 . . ..dynamics of (Platford) . . . . . .+Water (Rochester & Wilson)Water+ t-Butylalcohol (Pointud & Juillard) .. .Khurma) . .of Methane and Ethene: Thermodynaniics of Liquid (Calado & Soares) : : , .Neutron Inelastic Spectroscopy: Different Species of Hydrogen Chemisorbed on Raney NickelStudied by (Renouprez, Fouilloux, Coudurier, Tocchetti & Stockmeyer). . . .NH,-Chabazite: Thermal Stability of (Beyer, Jacobs, Uytterhoeven & Till)Nickel Ions in Silica-Magnesia: Kinetics of the Hydrogen Reduction of (Briend-Faure &"Peroxide" by Thermal Ahalysis : Inv&tigakon of the 'Decomposition Ad Reduciion of(Bond &Tripathi) . . . . . .under Steam Reforming Conditions: Reorg&isatibn of'(Moayeri & Trimm) . . .NiO and (Ni, Fe)O from 800-1200°C: Diffusion Enthalpies and Entropies in ThermallyForming (Tomlinson) .. . . . .Nitrates: Reaction of Oxygen Atoms with Met'hyl and Ethyl (Salter & Thrush) . . .Nitric Oxide in Aqueous and Nonaqueous Solvents: Solubility of (Shaw & Vosper) . .Nitrogen on Tungsten: Interaction of Diatomic Molecules with Clean Metal Wire Surfaces.Part 2.- (Couper & John) . . . .Nitromethane and with Nitroethane: Reaction of Oxygen Atoms with (Salter & Thrush) :Nitroxide with Alkanols : E.S.R. Measurements : Interaction of Di-t-Butyl (Atherton, Manter-field, Oral & Zorlu) .with Methanol. An Analysis of an Ac'cepto;: Self' Associated'Dondr Equ&brium: EiectronSpin Resonance Study of the 1 : 1 Hydrogen-Bonded Complex of Di-t-Butyl- (Bullock&Howard) . . . . .Non-Aqueous Solvents: Application of the Preisure-Jump 'Technique 'to the Measurement ofRates of Fast Reactions in (Buschmann, Knoche, Day & Robinson) .. . .Solubility of Nitric Oxide in Aqueous and (Shaw & Vosper) .Part 13.-Thermochemical Studies of some 1 : 1 electrolytes in Teframefhylurea : Physico:Chemical Studies in (Paul, Jauhar, Banait & Narula) .Nonpolar Solvents : Proton Magnetic Resonance Investigations of Nonionic PolyoxyethyleneNonylphenol Surfactant Aggregates in (Sheih & Fendler) .Nuclear Magnetic Relaxation of Alkali Halide Nuclei and Preferentiai Solv&ion in MeihanoiNuclear Magnetic Resonance and Sorption Experiments : Interpretation and Correlation ofStudies of Liquid Crystal Phase Structure and Self-diffusion Coefficients in' the SystemStudies of the Tetrahydroborate Anion in various Pure Solvents and' Binary AqueousMixtures : Solvation Spectra.Part 53.-Infrared and (Strauss, Symons & Thompson) .Nucleation and Growth of Pigment Dispersions Using a Laser Light-Scattering Apparatus inNumerical Estimation of Equilibrium Concentrations (Daul & Goel) ,. .Dela fosse)+Water Mixtures (Holz, Weingartner & Hertz) . . . .Zeolitic Diffusivities Obtained from (Karger & Caro) .Lithium Perfluoro-octanoate+ water (Tiddy) . . . .a Flow System: Studies of the Kinetics of (Nobbs & Patterson) . . . . .00- Ions on the Surface of Magnesium Oxide: Reaction between Ethylene and (Taarit, Symons& Tench)Olefin Polymerization on a Supported Ziegle; Catalyst: 'Kinetic Studies 'of (Eley, Keir &Rudham) ..Order-Disorder Tknsiti'ons in Substituted Adamantanes (Clark, Knox, Mackle & McKerveyjOrganic Compounds in Aqueous Solution. Part 3.--w-Amino acids and related compounds:Apparent Molal Heat Capacities of (Cabani, Conti, Matteoli & Tani) . . . .in Water. Part 1.-Ethers, Ketones, Esters and Alcohols: Partial Molar Volumes(Edward, Farrell & Shahidi) .in Water. Part 2.-Amines and Amides: Partial'Molai Voiumes 'of (Shahidi, Fariel1 &Edward) . . . . . . . . . . . . . .Oscillating Reaction to Addition of either Bromide or Cerium (IV) Ions: Response of theBelousov-Zhabotinskii (Blandamer & Roberts).Oscillation of the Belousov-Zhabotinskii Reaction : Analysis of ;he Dependence on Tempera-Oxidation.Part 4.-Hydroperoxide-Alcohol and Hydroperoxide-Ketone Transitions in theOxidation of Ethylbenzene : Sequence Studies in Liquid Phase Hydrocarbon (Danbczy,Nemes & GAl) .of Carbon Monoxide in Molten 'Carbonates. Confirmation of the Existence of the' COf'of Ethylal with C-14 as a Tracer: Slow Gas-Phase (Molera, Garcia-Dominguez, Rodriguez-L6pez and Santiuste)of Ferrous Sulphate Solutibns : Effect 'of Sulphuric Acid on the Cobalt-60 y-Ray Induced(Mat thews) . . . . . . . . . , . . . .ture of the Frequency of (Blandamer & Roberts) . . .Ion: Kinetics and Mechanism of Electrochemical (Borucka & Appleby) . . .of Dimethylaniline by Laponite : Adsorption and (Vansant & Yariv) . . .11111905545124513341098123996120254304656751239833148071136317311253558985114917381224476705715163610561351420181519005216 SUBJECT INDEX-VOLUME 73, 1977of Furan to Maleic Anhydride: Similarity in the Reactivity of 0; and Double Bond Typeof Hydrogen at 1 Atmosphere Pressure, 306 K : Kinetics of the Chlorine-Photosensitizedof Oxalate Ion: Photoelecirocatalysis 'by Metal Phthaiocyanine Eiaporated Films 'in theof 1-Phenylethanol in the Presence of Cobait Acetylacetonate's (Vasviiri & Galjof Propan-2-01 by Acid Chromate: Photoinduced (Klaning) .Oxygen Atoms with Methyl and Ethyl Nitrates: Reaction of (Salter & Thrush) :Atoms with Nitromethane and with Nitroethane: Reaction of (Salter & Thrush)Electrode.Part 8.-Oxygen Evolution at Rutherium Dioxide Anodes : The (Burke;in Copper-Cystamine Aqueous Solutions : €$omogeneous Catalysis of Cathodic ReductionLattice Oxygen as Revealed by Vapour-Phase Catalytic (Akimoto & Echigoya)(Cox & Derwent) ..(Meshitsuka & Tamaru) .. ...Murphy, O'Neill & Venkatesan) .of (Bettelheim, Faraggi, Hodara & Manassen) . . .. .PPalIadium/Rhodium and Palladium/Platinum Alloys : Thermodynamics of Hydrogen DissolvedPartial Molar Volumes of Organic Compounds in Water.' Pari 1 .-Ethers, Ketones, 'Ester;and Alcohols (Edward, Farrell & Shahidi)of Organic Compounds in Water. Part 2.-Amines and Amides (Shahidi, Farreli & Edward)Particle Sizes in Zeolites: Redox Behaviour of Transition Metal Ions in Zeolites.Part 5.-Method of Quantitative Determination of Bidisperse Distributions of Metal (Jacobs,Linart, Nijs, Uytterhoeven & Beyer)Particulates using the Patchwise Adsorption Modei: Deiermination 'of the Surface Hetero:geneity of Solid (House & Jaycock) . .Partition: Hydration and Dimerization of Some Aiiphati'c Carboxylic Acids in' Benzene asStudied by (Fujii & Tanaka) ,Passivation of Nickel. An X-ray Photoelectron 'Spec&oscopic Study:' Dissblutioh and(Dickenson, Povey & Sherwood) .Periodic Disc Electrode Forcing Functions : Ring-Disc Electrodes. Part 1 ?.-Ring Responseto (Bruckenstein, Tokuda & Albery) .Perturbation Method for Incorporating the Concent;ation' Dependende of t'he Flory-HugginsParameter into the Theory of Steric Stabilization (Evans & Napper) .. . .Perylene Anion: E.S.R. Study of Ion Pairs Involving the (Claridge & Kirk)Phase and Coordination Equilibria in Three-Component Systems of the Type MBr, +PyridineStructure and Self-diffusion Coefficients in the System Lithium Perfluoro-octanoate+ water:1,lO-Phenanthroline: Photoreduction of (Bandyopadhyay & Harriman)Phenol in Carbon Tetrachloride Solutions : Hydrogen-bonded Complexes *between Pyridine1-Phenylethanol in the Presence of Cobalt Acetylacetonatei: Oxidation of (Vasviri & Gal) :pH on the Emission and Absorption Characteristics of 2,3-Dicyano-p-hydroquinone : Effect ofPhotochemistry and Radiation Chemistry of 9,10~Anth~aquinone-2-sodium sulphonate in. .Photo-effects on Benzoylferrocene in Hydroxylic Solvents (Heaney, Logan & Powell) .Photoelectrocatalysis by Metal Pthalocyanine Evaporated Films in the Oxidation of OxalatePhotoelectrochemical Reactions over Metal Phthalocyanine Eiectrodes : Spectral Distribu:Photoinduced Oxidation of Popan-2-01 by Acid Chromate'(K1aning)Photoinitiating Systems based on Transition-Metal Carbonyl : Activities of Olefinic Deriiative;Photoinitiation of Polymerisation : Photolysis of Arene Chiomium Tricarbonyl and (Bamford;Photolysis of Alkyloxy Vanadium (v) Chelatks.A Possible 'Geneial Route to Alkyloxyof 3-Methyl-3-chlorodiairine (Frey &'Penny) *of Solutions Containing Maleimides : Electron Spin Resonance .Studies of' ElementaryProcesses in Radiation- and Photo-chemistry. Part 14.-(Ayscough, English, Lambert& Elliot) .. .Photophysical Behaviour : Airidine : An Investigation of its Moiecula; and Crystalline(Williams & Clarke) . . .in (Clewley, Lynch & Flanagan) . . . ... . .+Chlorobenzene (M = Mn, Co, Ni, Cu and Zn) (LibuS & Kluczkowski)Nuclear Magnetic Resonance Studies of Liquid Crystal (Tiddy) .. . .. * .and (Beezer, Hawksworth, Orban & Tyrrell) .(Brown & Porter) . . . .Aqueous Solution. Part 3.-Pulse and Gamma Radiolysis (Clark & Stonehill)of Michler's Ketone in Cyclohexane and Alcohol Solvents (Brown & Porter) .Ion (Meshitsuka & Tamaru) . . .tions of (Meshitsuka & Tamaru) . . . . .as Components of (Bamford & Mullik). . . .AI-Lamee & Konstantinov) .Radicals (Aliwi & Bamford) .. . . . . .Photoredox Reactions of Thionine iFerreira &' Harrirnan) . . .ECT INDEX-VOLUME 73, 1977Photoreduced States of Rhodamine €3 and Rhodamine 110; Triplet-Triplet Absorption-Photosensitized Oxidation of Hydrogen at 1 Atmosphere Pressure, 306 K: Kinetics of thePhotosynthetic and Related Polyenes : Singlkt - Triplet Intersystem Ciossing QuantumPigment Dispersions Using a Laser Light-Scattering Appaiatus in a Flow System: Studies ofPolarisable Spheres, with some Implications for “Structure” in Solutions : Theory oiElectrolytes. Part 2.-Tests of the Model of (Bennett0 & Spitzer)Polarograpby and Solvatochromism. Part 1 .-Polarographic Reduction of 5’-Meth&y-2’:hydroxy-N-methyl-4-stilbazolium Iodide and Related Compounds (Zuman & Szyper) .and Solvatochroism Part 2.-Comparison of Electrochemical and Spectral Properties of5’-Methoxy-2’-hydroxy-N-methyl-4-stilbazol~um Iodide (Szyper, Zuman & Gibson) .Polar Solvent Mixtures : Preferential Binding to Poly (a-L-lysine HBr) from (Komiyama, Mori,Yamamoto & Iijima) .. .Polyenes of Biological Interest : Absorption Spectra of Radical Ions of ’(Lafferty, Roach,Sinclair, Truscott & Land) . . .:Singlet ---t Triplet Intersystem Crossing Quantum Yieids of‘ Photbsynthetic &d Related(Bemasson, Dawe, Long & Land) .Polymer Catalysts: Heterogeneous Acid-Base Catalysis. Part 1 :-Ca;alysis‘of the Hydrolysisof Acetaldehyde Dimethyl Acetal (1 , 1-Dimethoxyethane) by Methacrylic Acid-divinyl-benzene Copolymer (a weak-acid ion-exchange resin), and the Characterization of (Gold& Liddiard) .:Photolysis of Arene Chromium Tricibonyis and Photohitiaiion of (Bakord, Al-Lamee &Konstantinov) .Polymerisation Reactions. Part 1 :‘Theory of Compartm&talised Free-Radical (Birtwistle dBlackley)Polymers: Determinatidn of Electr Anic Transf&ence’ Numbers of (Peh t & jozefiwicz) :Polyoxyethylene Nonylphenol Surfactant Aggregates in Nonpolar Solvents: Proton Magneti;Resonance Investigations of Nonionic (Sheih & Fendler)Poly (4-vinyl pyridine) with Ethyl, n-Propyl, n-Butyl, n-Hexyl i d Be&yl Biomide in Sdpho:lane: Kinetics and Mechanism of the Quaternization of (Boucher, Groves, Mollett &Fletcher)Porosity Changes ’in the Dehidration of ‘Calcium Sulphate Dihidrate’: Studies in the SystemCalcium SulphatelWater.Part 5.Purface Area and (Ball & Norwood)of Six Powders by Measurement of Nitrogen Sorption Isotherms: Study of ;he Effect ofCompaction on the Surface Area and (Gregg & Langford). . . . . .Porous Solids: Melting of Ice in (Rennie & Clifford).Potentials of the Silver-Silver Chloride Electrode in the Acetonitrile+ Ethylene Giycol Solven;System at 25°C: Studies in Isodielectric Solvents. Part 1.-Standard (Bose & Kundu).Potentiometric Studies of some Lanthanide Glycollate Systems (Carpenter, Monk & Whewell)Prediction of Infinite Dilution Activity Coefficients in Binary n-Alkane Mixtures (Lamb,Martire & Purnell) . . .Pressure: Conductance of Beryllium Sulphate Solution at’High’(Hsieh, h g & Changj :-Jump Technique to the Measurement of Rates of Fast Reactions in Non-Aqueous Solvents:Application of the (Buschmann, Knoche, Day & Robinson) .. .:Molar Conductivity of (n-butyl),N+(n-butyl)fi- as a Function of Temperature and (SpeedyjPromoted Chromia+ Alumina Dehydrogenation Catalysts : Heterogeneous Structures in(Masson, Bonnier, Duvigneaud & Delmon)Proteins at 9.9 GHz: Dielectric Properties of Hydrat‘ed (Bone, Gascoine &‘Pethig) .Proton Chemical Shifts of Hydrogen Bonded Complexes of Acetic Acid. Electric FieldCalculations for the Monomer-Dimer Shift and for Complexes with Fluoride or AcetateAnions (Akitt) .Proton-Donating Ability of Water h Hydrogeb-bonding Reactions : Note on the (Chiistian;Tucker & Mitra) .. . . . .Protonic Conductivity in Copper Formate Tetkthydrate (Murphy & Flanagan) . . .Sites in Highly Exchanged EZeolites : Inoperative (Ballivet & Barthomeuf)Proton Magnetic Resonance Investigations of Nonionic Polyoxyethylene NonylphenoiSurfactant Aggregates in Nonpolar Solvents (Sheih & Fendler) .Proton Transfer, Electron Transfer and Electronic Excitation : Generaliskd Fonter ‘Cycle:Thermodynamic and Extrathermodynic Relationships Between (Grabowski & Ruba-szewska) . .Protoporphyrin IX Dimkthyl Ester: Reaction of‘ the Triplet with &rotenoids : Excited St‘ates of(Chantrell, McAuliffe, MUM, Pratt & Land) . .Pulse hdiolysis of Acetonitrile : Kinetic and Thermodynamic Characier of Reducing Specie;;Produced on (Bell, Rodgers & Burrows) .. . . . . . . .of 3,4Dihydroxytoluene (Gohn & Getoff) . . . . . . . . .Spectra and the Spectra of the ( D u e & Quinn) . . . . .Photoreduction of 1,lO-Phenanthroline (Bandyopadhyay &‘Harriman) . .Chlorine (Cox & Derwent) . .Yields of (Bensasson, Dawe, Long & Land)the Kinetics of Nucleation and Growth of (Nobbs & Patterson). . .18 SUBJECT INDEX-VOLUME 73, 1977PAGEof Methanolic Solutions of Tetranitromethane (Johnson & Salmon) . 256Study of the Reaction of Solvated Electrons with Sulphur Hexafluorihe in' MethanolicSolution (Johnson & Salmon) . . 2031Pyridine and Phenol in Carbon Tetrachloride Sblutions : Hydrogen-bonded' Complexesbetween (Beezer, Hawksworth, Orban & Tyrrell) .. . . 1326QQuantum Yields of Photosynthetic and Related Polyenes : Singlet 3 Triplet IntersystemCrossing (Bensasson, Dawe, Long & Land) . 1319Quaternization of Poly (4-vinyl pyridine) with Ethyl, n-Propyl, n-Butil, n-Hexyl 'and Ben$Bromide in Sulpholane: Kinetics and Mechanism of the (Boucher, Groves, Mollett &Fletcher) . . 1629Quenching of Pyrene Sulphonate Fiuorescence 'in Inierse Micelles (Miller, Klein & Hauser) . 1654RRadiation and Electron Spin Resonance Study : Solvation Spectra. Part 52.-The Aquation ofSilver Atoms and Cations: a (Brown & Symons)and Photo-chemistry. Part 14.-Photolysis of Solutions Containing Maleimides.:Electron Spin Resonance Studies of Elementary Processes in (Ayscough, English,Lambert & Elliot)..Chemical Systems : Reactions of kydrdgen At oms'and Aliphatic Radicals' with 'Mondvalen;Cadmium and Nickel Ions as a Source of Hydrogen Yield in Some (Freiberg &Meyerstein) .Chemistry of 9,10-Anthraquinone-2-sodium~ Sulphonate in Aqueous Soiution: Pait 3.-Pulse and Gamma Radiolysis : Photochemistry and (Clark & Stonehill)Radical: Dissociation of 2-Methylbut-1-ene and the Resonance Energy of the 2-Methi1 allyi(Trenwith & Wrigley) . .Radical Ions of Polyenes of Biological Interest : Absorphon Spectra of ilaffeky, Roach:Sinclair, Truscott & Land)Radicals from CHC12CN and CHiClCN: Effect or Cyano-group Substitution on Rates o'fMetathetical Reactions.Part 2.-Abstraction of Chlorine Atoms by Cyclohexyl(Gonen, Horowitz & Rajbenbach) .in Vinyl Acetate: Evidence for Tunelling: Isotope Effeit in Hydrogen Atom 'Abstiactioifrom Substituted Phenols by Polyvinyl Acetate (Simonyi, Fitos, Kardos, KovAcs,Lukovits & PospiSil)Radiolysis of 3,4-Dihydroxytoluene: Pulse (Gohn &'Getoff)7-Radiolysis of Methane Adsorbed on y-Alumina. Part 1 .-Development 'of Sites Aciive inEnergy Transfer (Norfolk & Swan) .Radiolysis of Methanolic Solutions of Tetranitromet'hane :' Pulse' (Johnson & Salmon)Raman Spectroscopic Study: Thiocyanate Adsorption and Corrosion at Silver Electrodes. ARare-earth Activators Embedded in the Catalyst Lattice : Chemiluminescence during Catalysis.Part 2.-Luminescent Transitions of some (Aras, Breysse, Claudel, Faure & Guenin) .Rate Constant and Activation Energy : Kinetics of Electron Transfer Reaction betweenManganate and Permanganate Ions.Calculation of (Doh, Dogonadze & German) .Rate Constants for Singlet and Triplet Methylene : Flash Photolysis of Ketene. PhotolysisMechanism and (Pilling & Robertson)Rates of Fast Reactions in Non-Aqueous Solvents: Application of the PrkssurelJumpTechnique to the Measurement of (Buschmann, Knoche, Day & Robinson).of SNl-Type Solvolysis Reactions of Metal Complexes in Water+ Co-solvent Mixtures :Influence of the Solvent on the (Wells) .7-Ray Induced Oxidation of Ferrous Sulphate Solutions. Effeit of 'Sulphuric Acid on theCobalt-60 (Matthews)(RDX): Mass Spectrometric Study of the'Thermal Decomposition of 1',3,5-Trinitrbhexahydro:Reaction between Ethylene and 0- Ions on the Surface of'Magnesium Oxide (Taarit, Symonsof Cob(r)alamin with Nitrous Oxide and Cob(u)aiarnin'(Blackburn*, Kyaw & Swallow)'of Hydrogen Atoms with Ethane: Mass Spectrometric Study of the (Jones, Morgan &of Oxygen Atoms with Nitroethane and Nitromethane (Salter & Thrush):(Cooney, Reid, Fleischmann & Hendra) .. . .. ..1,3,5-triazine (Bradley, Butler, Capey & Gilbert)&Tench) . . .Purnell) . . ... .of Oxygen Atoms wit'h Methyl and Ethyl Nitrates iSalte; & Thrushj . .Reactions of Hydrogen Atoms and Aliphatic Radicals with Monovalent Cadmium and NickeiIons as a Source of Hydrogen Yield in Some Radiation Chemical Systems: (Freiberg &Meyerstein) .Reactivity of Zeolites Tipe H:Y and Na-Y with Meihanoi: Surface (Salvador & Kladnig)Recombination of Atoms.'Theory of the Smith-Linnett Method : Heterogeneous (Jablorisk;)SUBJECT INDEX-VOLUME 73,1977Redox Behaviour of Transition Metal Ions in Zeolites.Part 5.-Method of QuantitativeDetermination of Bidisperse Distributions of Metal Particle Sizes in Zeolites (Jacobs,Linart, Nijs, Uytterhoeven & Beyer) . . . .Behaviour of Transition Metal Ions in Zeolites. Part 6.-Reversibility of the ReductionReaction in Silver Zeolites (Jacobs, Uytterhoeven & Beyer) . . .Reduction of 5’-Methoxy-2’-hydroxy-N-methyl-4-stilbazolium Iodide and Reiated Compounds : .of Nickel Ions in Silica-Magnesia: Kinetics of the Hydrogen (Briend-Faure & Delafosse) .of “Nickel Peroxide” by Thermal Analysis : Investigation of the Decomposition and (BondRelaxation of Alkali Halide Nuclei ‘and Preferential Solvat’ion in’ Methanol Water Mixtures.Reorganisation of Nickel under Steam Reforming Conditions (Moayeii & TrimmjResonance Energy of the 2-Methyl ally1 Radical: Dissociation of 2-Methylbut-1-ene and the(Trenwith & Wrigley) .Fthodamine B and Rhodamine 110:’Triplet-Triplet AbsoGtion Spectra and ’the Spectra’of thePhotoreduced States of (Dunne & Quinn)Rhodium Catalyst for the Carbonylation of Monohydric ‘Alcohols : Selectivity df a Hetero:geneous (Christensen & Scurrell) .. . . . . . . . .Ring-Disc Electrodes. Part 17.-Ring Response to Periodic Disc Electrode Forcing Functions(Bruckenstein, Tokuda & Albery) .. .Rubrene Dissolved in Benzonitrile in Thin Celis : El&trochemi&l Luminescence of (Dunnett& Voinov) . . . . . . . . . .Ruthenium Blacks: Transformation of some Saturated Hydrocarbons on Iridium, Rhodiumand (Shrkhny, Matusek & Tktknyi) .Dioxide Anodes : The Oxygen Electrode. Part 8.-Oxygen Evolution at‘ (Burke, Murphy,O”eil1 & Venkatesan) . .Rutile: Infrared Study of the Adsorption of [zH4] Adetic Acid on to (Griffiths & Rochester) .Infrared Study of the Adsorption of Hexafluoroacetone on to (Griffiths & Rochester). .Infrared Study of the Adsorption of Water on to the Surface of (Griffiths & Rochester) .Polarography and Solvatochromism. Part 1 .-Polarographic (Zuman & Szyper) .& Tripathi) .Nuclear Magnetic (Holz, Weingartner & Hertz) .. ... .SSaturated Hydrocarbons on Iridium, Rhodium and Ruthenium Blacks : Transformation ofSelfdiffusion Coefficients in the System Lithium Pekuoro-octanoatek Wat‘er : Nuclear Mag-netic Resonance Studies of Liquid Crystal Phase Structure and (Tiddy)Semiconducting Oxides. The Effect of Prior Annealing Temperature on Dissolut‘ion Kineticsof Nickel Oxide (Jones, Segall, Smart & Turner) .Sequence Studies in Liquid Phase Hydrocarbon Oxidation. Par; 4.-Hydroperox~de-Alcohoiand Hydroperoxide-Ketone Transitions in the Oxidation of Ethylbenzene (Dank-,Nemes & Gal) . .Silica-Alumina Gels as a’Func;ion 0; Chemical Composition : Infiared kpprdach : Evoluiion OFthe Acidic Properties of (Scokart, Declerck, Sempels & Rouxhet)-Alumina Gels as a Function of Chemical Composition. Titration and ‘Catalitic Activit;Measurements : Acidic Properties of (Damon, Delmon & Bonnier)Immersed in Liquid Mixtures of Hydrocarbons: Infrared Study of the Surface of (Rocheste;&Trebilco) .. .-Magnesia: Kinetics’ of the Hydrogen Reduction of’ Nickel Ions in (Briend-Fake bDelafosse) .-supported Nickel: Infrared Study of the Adsorption of’Sulphur Cdmpounds on Silica and(Rochester & Terrell) . . .Silicon Subchlorides SiCl(g), SiCl,(g) and SiCl;(g) : Mass Spectrometric Deferminat ion of theHeats of Formation of the (Farber & Srivastava)Silver Electrodes.A Raman Spectroscopic Study : Thiocyanate ‘Adsorption- and Corrosion a;(Cooney, Reid, Fleischmann & Hendra) .SingIe Crystals: Thermotransport of Manganese Ions’in Sodium Chloride (Williams & Allnatt jSinglet Methylene with Methylenecyclopropane. Part 2.-High Energy Reaction Pathwaysfor Chemically Activated Insertion Products: Reaction of (Clements, Frey & Walsh) .4 Triplet Intersystem Crossing Quantum Yields of Photosynthetic and Related Polyenes(Bensasson, Dawe, Long & Land) . .Smith-Ewart Equations for Emulsion Polymerization Kinetics : Generai Solution lo the(Hawkett, Napper & Gilbert) .SNl-Type Solvolysis Reactions of Metal Cornpiexes in Waier + Co-salient Mixtures : Influenceof the Solvent on the Rates of (Wells) .Sodium Chloride Single Crystals : Thermotransport oi Manganese Ions’in (Williams & AllnattjAS of Transfer from Water to Mixtures Containing up to 40% Urea: Alkali Metal andAmmonium Chlorides in Water+Urea Systems.dG, AH, (Pointud & Juillard)some (SArkBny, Matusek & TktCnyi) . . ..20 SUBJECT INDEX-VOLUME 73, 1977PAGESolid Solutions. Part 1 .-Cation Distribution of Co2+ Ions: Structure and Catalytic ActivityPart 3.-E.S.R. Characterization: Structure and Catalytic Activity of Iron Oxide andSolid State Properties of Copper Containing Spinel Solid Solutions (Cu,Mg;-,A1~04) (SharpeReversible Temperature Dependent Spectral' Shift'in the Infrared Spectrum of DNA (NajSolubility of Nitric Oxide in Aqueous and Nonaqueous Solvent's (Shaw & Vospei)Sohbikation in Micelles.Part 4.-Studies on Cationic Micelles with added Electrolyte andon Lecithin Vesicles : Excimer Formation and the Ham Effect : Absorption and EmissionStudies of (Dorrance & Hunter) .Solute Interactions in Dilute Solutions. Pait 2.1A S;atistical Mkchanical Study of theHydrophobic Interaction (Clark, Frmks, Pedley & Reid) .in Dilute Aqueous Solutions. Part 3.-Volume Changes Associated with'the Hydro-phobicInteraction (Franks) . . . . . . .-Solvent Interaction in Water+ t-Butyialcohol Mixtures. Part 9.-Enthalpies of Tiansfe;for KBr, KI, Hl3r and HI (Pointud & Juillard).:Binding-induced Conformational Transition of Sodium Poly-L-Glutamate by Iron(rir):Effects of Ionisation on Adsorption from (Rendail & Smith)'of Hydrogen in Metals: Application to Pd/H(D): Isotope E&ct for thi (Oaies &of two forms of DL-a-Amino-n-butyric Acid in Water: Thermodynamics of (Abraham,Part 15.-Theoretical Treatment of Parailel First-Order 'Cataiysed .and UncaialysedSpectroscopy of the Bromide Ion: Far-Ultraviolet (Fox & Hayon).of C0,Mgl-,A1204 Spinel (Angeletti, Pepe & Porta).I .Magnesium Oxide (Cordischi, Pepe, Schiarello & Valigi) .& Vickerman) . . .in the Dry (Rossiter) . .. .Solution at High Pressure: Conductance of Beryllium Sulphate iHsieh, Ang & Chang) :Complex Ions in (Branca & Pispisa)Flanagan) . . . . . . . . . . . . .Ah-Sing, Marks, Schulz & Stace) .Reactions : Heterogeneous Catalysis in (Spiro) .. . . . . .of the Iodide Ion: Far-Ultraviolet (Fox & Hayon)Solutions of Lithium Salts in Liquid Lithium. The Electrical Resistivit; of Solutions ofNitride, Hydride and Deuteride (Adams, Down, Hubberstey & Pulliarn)(Cu,Mgl-,AI20,) : Solid State Properties of Copper Containing Spinel Solid (Shaipe &Vickerman) .of Tetranitromethane': Pulsk Radiolysis of Methan'olic (Johnson & Salmon):Termination Errors in Fourier Analysis of Diffraction Data of Aqueous Elecirol yte(Triolo & Ruffo)Solvated Electrons with Sulphur Hekfluoride in Meihanok Solution I Pulse Radiolysis Studyof the Reaction of (Johnson & Salmon) .Solvation in Methanol+ Water Mixtures : Nuclear' Maketic Relaxation. of Aikali 'WalidkNuclei and Preferential (Holz, Weingartner & Hertz).Spectra.Part 52.-The Aquation of Silver Atoms and Cations: a Radiation and EiectronSpin Resonance Study (Brown 8& Symons) .Part 53.-Infrared and Nuclear Magnetic Resonance' Studies of the 'TetrahydroborateAnion in various Pure Solvents and Binary Aqueous Mixtures (Strauss, Symons &Thompson) . . . .Part 54.-A Low Ternperaiure Infrared Spectroscopic Study' of the Sokation of Ions inMethanol (Strauss & Symons).Sdvatochromism . Part 1 .-Polarographic Reduction of 5'-Me;hoxy~2'-hydroxy:N-me;hyl-4-stilbazolium Iodide and Related Compounds: Polarography and (Zuman & Szyper) .Part 2.-Comparison of Electrochemical and Spectral Properties of 5'-Methoxy-2'-hydroxy-N-methyl-4-stilbazolium Iodide : Polarography and (Szyper, Zuman & Gibson)Solvent Mixtures : Preferential Binding to Poly (E-L-lysine HBr) from Polar (Komiyama, Mori,Solvents.Part 1 .-Standard Potentials of the Silver-Silver' Chloride 'Electiode in thiAcetonitrile+Ethylene Glycol Solvent System at 25°C: Studies in Isodielectric (Bose &Kundu) . . . .Part 13.-Thermochemical'Studi'es of 'some '1 : 1 electrolytes in Tetramethylurea: Physico:ChemicaI Studies in Nonaqueous (Paul, Jauhar, Banait & Narula)Sorption Experiments : Interpretation and Correlation of Zeolitic Diffusiviiies obtained fromNuclear Magnetic Resonance and (Karger & Caro) . .Isotherms: Study of the Effect of Compaction on the Surface Aiea an'd Poiosity'of Sixof Water Vapour by some Derivatives of Bovine Serum Albumin (Rochester & WestermanjSpectral Distributions of Photo-electrochemical Reactions over Metal PhthalocyanineProperties of 5'-Methoxy-2'-hydroxy-N-nie~hyl-&stilba~olium Iodide : Polarography andSolvatochromism.Part 2.-Comparison of Electrochemical and (Szyper, Zuman &.;..Yamamoto & Iijima) . .Powders by Measurement of Nitrogen (Gregg & Langford)Electrodes (Meshitsuka & Tamaru) .Gibson) . . . . . . . . . . . .SUBJECT INDEX-VOLUME 73, 1977Shift in the Infrared Spectrum of DNA(Na) in the Dry Solid State: Reversible TemperatureSpectrophotometric Investigations 'in Aqueous Soiution' at Elevated Temperatures. TheEffect of Temperature on the Ionisation Constant of the 2,2' Bipyridyl Cation (Buisson& Irving)Spectroscopic and Dielectric Propekes df Solutions' of Et'hanoi in Cyclohexane in Teims ofAssociation: Interpretation of the Thermodynamic (Stokes)Spinel Solid Solutions.Part l.-Cation Distribution of Co2+ Ions: Struciure and CatalyticActivity of Co,Mg,-,A120a (Angeletti, Pepe & Porta)Solid Solutions (Cu,Mg,-&,O4): Solid State Properties of Coppe; Con'taining (Sharpe &Stability of Metal Uncharged Ligand Complexes in Ion Exchangers. Part 1 .-QuantitativeCharacterization and Thermodynamic Basis (Maes, Marynen & Cremers) . . .of NH4-Chabazite: Thermal (Beyer, Jacobs, Uytterhoeven & Till) .Static System: Hydrogenation of Acetylene in Excess Ethylene on an Aiumina SupportedPalladium Catalyst in a (McGown, Kemball, Whan & Scurrell) .Statistical Mechanical Study of the Hydrophobic Interaction: Solute Interactions in DilutiSteam Reforming Conditions : Reorganisation of Nickel under (Moaykri & Trimm)Steric Stabilization: Perturbation Method for Incorporating the Concentration Dependence ofthe Flory-Huggins Parameter into the Theory of (Evans & Napper) .Structure and Catalytic Activity of Co,Mg1-,Al~O4 Spinel Solid Solutions.Part 1 .-Cationand Catalytic Activity of Iron Oxide and Magnesium Oxide Solid Solutions: Part 3.-in Solutions: Theory of Electrolytes. Part 2.-Tests of the Modei of P&isable Spheres;of Aquo-alcoholic Solvents : Transfer Free Energies and Entropies of Hydrobrdrnic Acid if;Ethanol+Water Mixtures: (Das, Bose & Kundu) . . . .Substitution on Rates of Metathetical Reactions.Part 2.-Abs&actioi of Chlorine Atoms byCyclohexyl Radicals from CHC12CN and CHzClCN: Effect of Cynano-group (Gonen,Horowitz & Rajbenbach)Sulphur-poisoning on the Adsorption of Carbon Monoiide by Nickel : Infrared Study ofEffects of (Rochester & Terrell) . * . . .Supported Palladium Catalyst in a Stat'ic System: Hydrogenation of Acetylene in ExcessEthylene on an Alumina (McGown, Kemball, Whan & Scurrell)Ziegler Catalyst: Kinetic Studies of Olefin Polymerisation on a (Eley, Keir & Rudham) ,Surface Area and Porosity Changes in the Dehydration of Calcium Sulphate Dihydrate:Area and Porosity of Six Powders by Measurement of Nitrogen Sorption Isotherms: Study ofChemi-ionisation: Molecular Beam Study of (Normingion, Bomse & Grice) : Heterogeneity of Solid Particulates using the Patchwise Adsorption Model : Determinationof Magnesium Oxide: Reaction of Ethylene-and 0- Ions on ;he (Taarit, Symohs & Tench)of Silica Immersed in Liquid Mixtures of Hydrocarbons: Infrared Study of the (Rochester& Trebilco) .. . . .Reactivity of Zeolites Type H-Y'and Na-Y with Methanol (Salvador & kaddig) .Surfaces: Comparison of Theory and Experiment: van der Waals Interaction between Mica(Gregory) . . .Part 1 .-Hydrogen on Tungsten :'Interaction of Diatomic Molecules' with Clean Metal Wiri(Couper & John) . . . .Part 2.-Nitrogen on Tungsten : kteraction of Diatomic Molkcules'with Clean' Metal WireKinetics of Adsorption on Energeticaliy Heterogeneous ?Crickmore & Wojciechowski)'Surfactant Aggregates in Nonpolar Solvents : Proton Magnetic Resonance Investigations ofSurfactants from Water to Water+ Acetone Mixtures from Vapour Pressure Measurements :Standard Free Energy of Transfer of Ionic (Treiner & Le Besnerais) .. . .Dependent (Rossit er) . . .Vickerman) . . . . . . . . . . .. .Solutions. Part 2.-A (Clark, Franks, Pedley & Reid) . . . .Distribution of Co2+ Ions (Angeletti, Pepe & Porta) . . .E.S.R. Characterization (Cordischi, Pepe, Schiavello & Valigi)with some Implications for (Bennett0 & Spitzer). .Studies in the System Calcium Sulphate/Water. Part 5.- (Ball & Norwood)Effect of Compaction on the (Gregg & Langford) . .of the (House & Jaycock) ..(Couper & John) .Nonionic Polyoxyethylene Nonylphenol (Sheih & Fendler) .. . . .TTemperature and Pressure : Molar Conductivity of (n-b~tyl)~N+(n-butyl),B- as a function of(Speedy)Dependence of the bieraction Second Virial 'Coefficient using Gas-Liquid Chromatograph;(Neogi & Kudchadker) . .Dependent Spectral Shift in the Infrared Spectrim ofDNA(Na)'in the Dr; Solid Stat;(Rossiter) . . . . . . . . . . . . .22 SUBJECT INDEX-VOLUME 73, 1977PAGEof the Frequency of Oscillation of the Belousov-Zhabotinskii Reaction: Analysis of theTheoretical Aspects of Hydration Isotherms for Biomolecules : -Expehmenial and (GakoyneModels: Kinetics of Activated Chen&orption. Part 2:- (Aharoni & Ungarish)Theory of Compartmentalised Free-Radical Polymerisation Reactions.Part 1 (Birtwistle &of Electrolytes. Par; 2.-Tests of the Modei of Pdlarisable Spheres; with some implicationsof Smith-Linnett Method : Heterogeneous Recombinatibn of Atoms (Jabfonski)Thermal Analysis: Investigation of the Decomposition and Reduction of “Nickel Peroxide” byDecomposition of 1,3,5-Trinitrohexah~dro-l;3,5-tr~azine*(RDX): Mass Spectrometric StudyDecomposition of Zinc Nitrate Hexahydrate : E.S.R. Investigation of the (Campbeli)Decompositions of 2,2’-Azoisobutane and Azoisopropane : Comparison of the MechanismsGas-Phase Decomposition of 1,2-Epoxypropane: Kinetics of ;he (Floweis)Stability of NH4-Chabazite (Beyer, Jacobs, Uytterhoeven & Till)Dependence of (Blandamer & Roberts) .. .& Pethig) .Blackiey) .*for “Structure” in Solutions (Bennett0 & Spitzer)(Bond & Tripathi) . . . .of the (Bradley, Butler, Capey & Gilbert).. . .. .of the (McKay, Turner & Zark) . :Thermally Forming NiO and (Ni, Fe)O from 800-1 200°C : Diffusion Enthalpies a i d Eniropie;ThermochemicaI Studies of some ‘1 : 1 electrolytes’ in Tetramethylurea: Physico-ChemicaiStudies in Nonaqueous Solvents.Thermodynamic and Extrathermodynamic Relationships Between Proton Transfer, ElectronTransfer and Electronic Excitation : Generalised Forster Cycle (Grabowski &Rubaszcwska)Character of Reducing Species Produced on Pulse Radiolysis of Acetonitrile: Kinetic andFunctions for the System Ethanol+ Cyclohexane from Vapoui Pressures and EnthaIpies ofProperties of Hydrogen in Palladium and its‘ Alloys under Conditions of ‘Cons;ant VolumeSpectroscopic and Dielectric Properties of Solutions of Ethanol in Cyclohexane in Teims ofStudy of the Vaporization of Cerium Orthophosphale (Guido, Balducci, D e Maria &Thermodynamics of Hidrogen Dissolved in Palladium/Rhodium and Palladium/Platinumof Liquid Mixtures of Methane and Ethene icalado & Soare;)of Miscible Liquid Mixtures of Carbon Tetrachloride, n-Octanol and Wa‘ter a; 20°Cof Solution of two iorms ‘of m-a-Amino-n-but& Acid in Water (Abraham, Ah-Sing,Thermolysis of 2-Ethyloxetan (Clarke & Ho1b;ook)Thermotransport of Manganese Ions in Sodium Chloride Single Crystals (William; & Allnat t jThin Cells: Electrochemical Luminescence of Rubrene Dissolved in Benzonitde in (Dunnett &Voinov) .. . f . Thiocyanate Adsorption‘and Corrosion at Silver Electrode‘s. A Raman Spectroicopic*Study(Cooney, Reid, Fleischmann & Hendra) .Thiols and Amines Hydrogen Bonding Type Charge Transfer Interaction between (Yarnabe:Akagi, Hashimoto, Nagatar & Fukui)Thionine: Photoredox Reactions of (Ferreira & HariimanjThree-Component Systems of the Type MBr,+Pyridine+Chlorobenzene (M = Mn, Co, Ni’,Cu and Zn): Phase and Coordination Equilibria in (LibuS & Kluczkowski) .Tracer Diffusion Measurements in Liquids : Closed Capillary Method for (Passhemi’,Liukkonen & Noszticzius) .:Slow Gas-Phase Oxidation of Ethylal with C-14 as*(Moiera, Garcia-Dominguez; Rodiiguez:L6pez & Santiuste) .Transference Numbers of Polymers; Detirrnination of Electroni; (Petit & Jozefowicz) :Transfer Free Energies and Entropies of Hydrobromic Acid in Ethanol+ Water Mixtures :Structure of Aquo-alcoholic Solvents (Das, Bose & Kundu)‘Transformation of some Saturated Hydrocarbons on Iridium, Rhodium and’ RutheriumBlacks (Sarkany, Matusek & TCtCnyi) .Transition-Metal Carbonyls : Activities of Olefinic’ Deribatives as Components of Photo:initiating Systems based on (Bamford & Mullik)Ions in Zeolites.Part 5.-Method of Quantitative Determination’ of Bidispeise Distribu:tions of Metal Particle Sizes in Zeolites: Redox Behaviour of (Jacobs, Linart, Nijs,Uytterhoeven & Beyer) . .Ions in Zeolites. Part 6.-Reversibility‘of the Reduction’ Reac‘tion in Silver Zeo‘lites: Redoxin (Tonilinson) .. . .Part 13.- (Paul, Jauhar, Banait & Narula) .(Bell, Rodgers & Burrows) . .Mixing (Stokes & Adamson) .(Oates & FIanagan) . . .Association : Interpretation of the (Stokes)Gigli) . . . . . . . . . . .Alloys (Clewley, Lynch & Flanagan)(Platford) . . . . . .Marks, Schulz & Stace) ..SUBJECT INDEX-VOLUME 73, 1977Transition of Sodium Poly-L-Glutamate by Iron(@ Complex Ions in Aqueous Solution:Binding Induced Conformational (Branca & Pispisa) .Transitions in Substituted Adamantanes : Order-Disorder (Clark, Knok, Mackle & McKerveyjof some Rare-earth Activators Embedded in the Catalyst Lattice: Chemiluminescenceduring Catalysis.Transport in Aqueous Solutions of Group IIB Metal Salts at 298.15 K.Part 1.-IsothermaiTransport Properties of Cadmium Iodide (Paterson, Anderson & Anderson)in Aqueous Solutions of Group IIB Metal Salts at 298.15 K. Part 2.-Interpretation andPrediction of Transport in Dilute Solutions of Cadmium Iodide: An Irreversible Thermo-dynamic Analysis (Paterson, Anderson, Anderson & Lutfullah).System GaAs-HBr Using a Modified Entrainment Method : Thermodynamic Study 'of thiChemical Vapour (Faktor, Garrett, Lyons & Moss) .Trapped Electrons in Mixed-Solute Aqueous Glasses : Luminescence Foilowing Laser Excitationof (Nguyen. & Walker) .Trapping Technique : Detection and Identification oi Organic Radicais Produced in the LowPressure Silent Electric Discharge by an Electron Spin Resonance Spin (Hibbert, Robertson& Perkins)Triplet and Singlet Meihylenk : Kinetics 'of Mkthylene Addition to cis- and tra&-But:2-ene'.Further Evidence for the Energy Separation between (Frey & Kennedy)Energy Transfer in 2-Methylpentan-2,4-diol: Viscosity Dependence of Diffusion-controlled(Dainton, Henry, Pilling & Spencer)Methylene : Flash Photolysis of Ketene.Photolysis Mechanism afld Rate Constants fo;Singlet and (Pilling & Robertson)-Triplet Absorption Spectra and the Spectra of the Photoreduced States' of Rhodamine Bwith Amines: Interaction of Duraquinone Lbwest '(Amdnyal & Beniasson)with Carotenoids: Excited States of Protoprophyrin IX Dimethyl Ester: Reaction of thi(Chantrell, McAuliffe, Munn, Pratt & Land)Tris-(Acetylacetonato) Derivatives of Aluminium(m), Gallium(ni) and Indi;m(mj: Enthalpiesof Combustion of (Cave11 & Pilcher) .. .Tunnelling: Isotope Effect in Hydrogen Atom Abstraction f;om Substituted 'Phenols byPolyvinyl Acetate Radicals in Vinyl Acetate : Evidence for (Simonyi, Fitos, Kardos,KovBcs, Lukovits & PospiSil . . . . . . .Part 2.-Luminescent (Aras, Breysse, Claudel, Faure & Guenin)....and Rhodamine 10 (Dunne & Quinn) . . . . .,VVanadium(v) Chelates. A Possible General Route to Alkyloxy Radicals: Photolysis ofAlkyloxy (Aliwi & Bamford) . - .van der Waals Interaction between Mica Surfaces: Comparison of Theory and ExperimentVaporization of Cerium Orthopho'sphate : Thkrmodynamk Study of the (Guido, Baiducci;De Maria & Gigli) .Vapour-Phase Catalytic Oxidation of F&an to'Maleic Anhydride: Similarity in the Reaitivit;of 0; and Double Bond Type Lattice Oxygen as Revealed by (Akimoto & Echigoya) .Pressure Measurements: Standard Free Energy of Transfer of Ionic Surfactants from Waterto Water+ Acetone Mixtures from (Treiner & Le Besnerais)Pressure of H,lsO Ice (-50 to OOC) and HzlsQ Water (0 to 170"Cj (Jakii & Siaschewski):Pressures and Enthalpies of Mixing: Thermodynamic Functions of the System Ethanol+Cyclohexane from (Stokes & Adamson) .Transport System GaAs-HBr Using a Modified' Entrainment Method I TheirnodynamicStudy of the Chemical (Faktor, Garrett, Lyons & Moss)Virial Coefficient using Gas-Liquid Chromatography: Temperatuie Dependence of theInteraction Second (Neogi & Kudchadker)Viscosities of Hexamethylphosphotriamide at 25°C : Electrolyte (Sacco; Petrella, Della Monica& Castagnolo)Viscosity Dependence of Diffusion-controlled Triplet Energy Transfer' in 2-Methylpentan-2,idiol (Dainton, Henry, Pilling & Spencer) .Volume Changes Associated with the Hydrophobic interaction:' Solutk Interactions in Dilute(Gregory).Aqueous Solutions (Franks) .. .WWater + Acetone Mixtures from Vapour Pressure Measurements : Standard Free Energy ofWater. Part 1 .-Ethers, Ketones, Esters and Alcohols: Partial Molar Volumes of Organ&Transfer of Ionic Surfactants from Water to (Treiner & Le Besnerais) .Compounds in (Edward, Farrell & Shahidi) .. . . . . .24 SUBJECT INDEX-VOLUME 73, 1977PAGEPart 2.-Amines and Amides : Partial Molar Volumes of Organic Compounds in (Shahidi,in Homoionic and Heteroionic Mordenites A Calorimetric-Study. Part 1 .:Alkali andin Hydrogen-bonding Reactions: Note on the Proton-Donating Ability of‘ (Chiistian,on to the Surface of Rutilei Infrared Siudy of the Adsoiption’of (Griffiths & Rochester) .Water +Urea Systems. dG, AH, d S of Transfer from Water to Mixtures Containing up toWater Vapour by some Derivatives of Bovine Serum Albumin: Sorption of (Rochester &Farreil & Edward) 71 5Alkaline Earth Metal Forms (Coughlan, Carroll & McCann) . . 161215101048Tucker & Mitra) .53740% Urea: Alkali Metal and Ammonium Chlorides in (Pointud & Juillard) . .Westerman) . . . . . . . . . . 33XX-ray Photoelectron Spectroscopic Study : Dissolution and Passivation of Nickel: AnSpectroscopy and Heterogeneous Catalysis, with Elimination Reactions as an Example(Dickinson, Povey & Sherwood) . . 327(Vinek, Noller, Ebel & Schwarz) . . . . 734YYoung’s Equation: On Deviations from (White) . . . . . 390Y-Type Zeolite: Determination of the Active Site and Mechanism for AIkene Isomerization inCuII Exchanged (John & Leach) . . . . . . 1595Zeolite-L: Exchange of Alkylammonium Ions in the (Vansant & Peeters) .Zeolite: Hydroisomerization and Hydrocracking of n-Pentane (3-C13) with Type Y (Wieks &Bolton) ,L-Zeolites: Inoperative ‘Protonic Sites in’Highjy Exchanged (Ballivet ’& Baithomeuf) :Zeolites X: Interpretation of the “Intermediate Frequency” Dielectric Spectra of Synthetic(Ravalitera, Carru & Chapoton) .Part 5.-Method of Quantitative Determ;hation of Bidisperse Distributions of ’MetalParticle Sizes in Zeolites: Redox Behaviour of Transition Metal Ions in (Jacobs, Linart,Nijs, Uytterhoeven & Beyer) .Part 6.-Reversibility of the Reduction in Silver Zeolites : Redox Behaviour of TrakitioiMetal Ions in (Jacobs, Uytterhoeven & Beyer) .Type H-Y and Na-Y with Methanol: Surface Reactivity of (Salvador & Kladnig)Zeolitic DiEusivities Obtained from Nuclear Magnetic Resonance and Sorption Experiments :Interpretation and Correlation of (Karger & Caro) ..Ziegler Catalyst: Kinetic Studies on Olefin Polymerisation on a Supported (Eiey, Keir &Rudham)AUTHOR INDEX-VOLUME 73. 1977Abraham. Michael H .Adanis. Paul F . .Adamson. MarionAharoni. Chaim .Ah.Sing. Eric .Akagi. KslzuoAkimoto. MasamichiAkitt. J . W . .Albery. W . John .Aliwi. Salah H . .Al.Lamee. Kadem G .Allnatt. Alan R .Aloisi. G . GaetanoAmouyal, EdmondAnderson. John .Anderson. Stephen S .Ang. K . P . . .Angeletti. Carlo .Appleby. A . JohnAras. Vilas M .Ashmawy. Fathy M . Atherton. Neil M .Aveyard. Robert .Ayscough. Peter B .Balducci. G . .Ball. Matthew C .Ballivet. Danielle . .Bamford. Clement H . .Banait. Jagtar S .Bandyopadhyay. Baida N .Barthomeuf. Denise .Beezer.Anthony E . .Bell. Ian P .Bennett0,H.P. . .Bensasson. Renato .Bensasson. RenC .Bettelheim. Armand .Beyer. I-Iermann K . .Birtwistle. David T . .Blackburn. Robert .Blackley. David C . .BIandamer. Michael J . .Bolton. Anthony P . .Bond. Geoffrey C . .Bone. Stephen .Bonnier. Jane-Marie .Borucka. Alina .Bose. KumardevBoucher. Ernest A . .Bradley. John N . .Branca. Mario .Breysse. Michele .Briend.Faure. MargueriteBrown. D . Robert . .Brown. Robert G . . .Bruckenstein. Stanley + Buisson. David H . .Bullock. Anthony T . .Burke. Laurence D . .Burrows. Hugh D . .Bomse. David S . . .PAGE 582SUBJECT INDEX-VOLUME 73, 1977 41PAGEMMagnetic Anisotropies from the Cotton-Mouton Effect: Molecular (Battaglia & Ritchie)Circular Dichroism Studies of Charge-Transfer-to-Solvent Spectra (El-Kovrashy &Grinter) .. . . . . .Manganate Ion: Electronic Spectrum of ;he Manganate (;) (Bo;romei, Oleari & Day).Mass Spectrometric Knudsen Cell Method and Discussion of the Dissociation Energies of theMolecules Se2(g), SSe(g) and SeTe(g): Determination by the (Drowart & Smoes)Knudsen Cell Method: Determination of the Atomization Energies of the Molecules CSe(gjMathematics of Wien Dissociation in Weak Electrolytes (McIlrdy & Hill) .Matrices at 10 K: Contact Charge Transfer Interactions between Aromatic Molecules andat 10 K: Energy Transfer Processes Involving Chromium Hexacaibonyl in Gas (Rest &Sodeau) . . . . . . . . . . .,Models for the Aggregation Processes: Cluster Formation in Rare Gas (Moskovits &Hulse) , .. . . . . .:Observations on the Electronic Spectra of Cud, Ago and AuO Isolated in Rare Gas(Griffiths & Barrow) . . .:Relative Quantum Yields for t'he Foimatibn and Des'tructibn of' Pentacarbonyl Molyb-Matrix Method for the Calculation of n-Electron Energies for Linea; Conjugated Polymers':Matrix : Proposed Iron-Nitrogen Molecule Produced in a Solid Nitrogen (Barrett & MontanojMelt: Q4-Dependent Broadening in Quasielastic Incoherent Neutron Scattering from a PolymerMetal Acetylacetonates : Anomalous Electric Polarizations and the Sub-miilimetre Spectra inMetastable Argon ( ~ S ~ P ~ , ~ ) to Xenon, Oxygen and Chlorine Atoms : Electronic EnergyMethane: Dispersion Forces in (Lekkerkerker,'Coulbn & Luyckx)Micelles.Part 3.-Fluorescence Polarization of Solubilisates in Citionfc Mkelles':Absorption and Emission Studies of Solubilisation in (Dorrance, Hunter & Philp)Ultrasonic Relaxation Studies of the Exchange Process Between Surface Active AgeniIons, Small Molecules and Mixed (Hall, Jobling, Wyn-Jones & Rassing)Microwave Spectroscopy : Some Molecular Properties of Carbonyl Bromide De'termined byMixed-Gas Adsorption. Localised Monolayer Adsorption on Heterogeneous Surfaces':Statistical Thermodynamics of (Jaroniec) .Mixtures of Linear and Branched Alkanes with 1,2-Dibromoethane A d Tetrahydronaphtha:lene. Part 1 .-Enthalpies of Mixing: Thermodynamic Properties of (Delmas & Purves)of Linear and Branched Alkanes with 1 ,ZDibromoethane and Tetrahydro-naphthalene.Part 2.-Free Energies and Entropies of Mixing: Thermodynamic Properties of (Delmas &Purves) ..MnO+NiO Solid Solutions: Thermodynamics of' MnO+CoO and (Catlow; Fender &Hampson) . . . . . .Mobile Adsorbates : Modified Statistical Treatment of Pariially iLyklzma) .Mobility and Reactivity of CO; and COY Species Adsorbed on MgO: E.P.R. Sfudies'of theStructure (Meriaudeau, Ben Taarit, Vedrine & Naccache) . . . . . .Model Fluid Mixture which Exhibits Tricritical Points. Part 2 (Desrosiers, Guerrero,Rowlinson & Stutley) . . . .for Intermolecular Forces : Some Appiications of a Self-Exch'ange Corrected Electron Gas(Lloyd & Pugh) . . . . .Models for the Aggegaiion P~ocesses: Ciuster Formation in Rare Gas Matrices (Moscdvits &Hulse) .. . . . . . . . . .Modulation Techniques:' Complete Polarisation Measurements in Resonance Raman Spectro-scopy Using Linear and Circular Polarisation (Horvath & McCaffery) .Molecular Beam Studies of Ethyl Nitrite Photodissociation (Tuck)Molecular Complexes ofp-Benzoquinone with Aromatic Bases. On the Evidence fbr LocalisedCharge Transfer: Infrared Spectra of (Alciaturi) . .thi(Craig, Rodgers & Wood) . .Molecular Crystals : Phonon Scattering and Exciton 'Linewidths in Napht'halenk andPhenanthrene (Dissado & Brillante). . . . .Part 2.-Structural Changes at Planar Faults-Their Importance in Facilitating Photo:dimerization and in Governing Stacking Fault Energies : ComputationaI Approach tothe Study of Extended Defects in (Ramdas, Thomas & Goringe) .. . . .and CSe2(g) by the (Smoes & Drowart) . . . . . .Oxygen in Gas (Rest, Salisbury & Sodeau)denum, MO(CO)~, in Low Temperature (Poliakoff) .Polynomial (Kaulgud & Chitgopkar) . .(Higgins, Ghosh, Howells & Allen) . . . . . .Solution of some (Haigh, Jinks, Sutton & Waddington) . . . .Transfer from (King, Piper & Setser) . . . . .(Carpenter, Smith, Thompson & Whiffen) . . .42 SUBJECT INDEX-VOLUME 73, 1977Molecular Dynamics Computer Simulation of Surface Properties of Crystalline PotassiumChloride (Heyes, Barber & Clarke) . . .of Viscous Liquids. A Comparison of Dielectric and'Kerrieffect ' Relaxation' for TritoyiPhosphate, orfho-Terphenyl and their Mixtures (Beevers, Crossley, Garrington &Williams) .. .Magnetic Anisotropies from the Cokon-Mouton Effect (Battaglia & kitchi;).Molecular Motion in Tertiary-butylammonium Chloride, Bromide and Iodide : Proton SpinLattice Relaxation Study of (Ratcliffe & Dunell)Molecular Number Densities : Torsional Oscillation in Liquid Chlorodenzene at High (EvansjMolecular Orbital Calculations of the Exchange Parameter for Copper(1r) CarboxylateDimers : Superexchange and some (Harcourt & Martin)Calculations of the Isomer Pairs HCN, CNH and FCN, CNF: Use of Parka1 LOwdiniPLA)and Limited Expansion of Diatomic Overlap (LEDO) Integral Approximation Methodsin (Doggett) . . .Energy Level Diagrams by the Method of 'Progressive Inteiactions of 'Atomic Or'bitals':Construction of (Dixon).Theory: Applications of the Cauchy Inequalities in Simple (Gutman & Trinajstik) ..Molecular Properties of Carbonyl Bromide Determined by Microwave Spectroscopy : SomeStructure of FS020F: Wide Line N.M.R. Analysis of tlie (Alien, Mkal1,'Aubke & Duneli)Mori Continued Fraction: Absorption of Dipolar Liquids in the Far Infrared: A SensitiveMeasure of the (Davies, Evans & Evans) . . . . ...:Non-empirical Calculations with Valence-shell (Vincent & Murrell) . .(Carpenter, Smith, Thompson & Whiffen)Monohydric Alcohols: Self-Diffusion in Water and (Pratt & Wakeham) . . .Multilayer Adsorption and Wetting: Note on (Richinondj : .. . .NNaphthalene, its Anion, Cation and Triplet : Electronic Structure and Properties of (Hinchliffe)-N(CH& and .- N+(CH& Groups in Dimethyl Aminophenols and their Methiodides :Nematic K21: High and Low Frequency Torsional Absorptions in (Eians & Evans)Liquid Crystal: Nuclear Magnetic Double Resonance Studies of Isotopically LabelledBis-(Dich1orophosphino)methylamino Partially Oriented in a (Colquhoun & McFarlane)Neutron Scattering from a Polymer Melt : Q4-Dependent Broadening in Quasielastic Incoherent(Higgins, Ghosh, Howells & Allen) .Molecular Reorientation in Three Orientationally Disordkred Moledular Crystals b;Incoherent (Leadbetter & Turnbull) .Characteristic Vibrations of (Agaste & Jose) . . ...Nitriles: Electron Impact Spectroscopy of Some Simple (Stradling & Londbn)Nitrosyl Halides: Photoelectron Spectra of (Alderdice & Dixon)Non-empirical Calculations with Valence-shell Molecular Orbitals (Vincent & Murrell) :Non-paired Spatial Orbital Wavefunction for Benzene: Ab inifio (Hirst)Non-polar Mixtures. Part 1. Computer Solution Techniques and Stability Tests I TheoieticaiPrediction of Phase Behaviour at High Temperatures and Pressures (Hicks & Young)Part 2.-Gas-gas Immiscibility: Theoretical Prediction of Phase Behaviour at HighPart 3.-Comparison with Upper Critical Solution Temperatures for Perfluoromethyi-cyclohexane+Hydrocarbons : Theoretical Prediction of Phase Behaviour at HighNuclear-Excited Feshbach Resonances. Part 5.-Effective Number of Degrees bf FreedomParticipating in the Sharing of the Ion's Excess Energy: Long-Lived Parent NegativeIons Formed via (Christophorou, Gant & Anderson).Nuclear Magnetic Double Resonance Studies of Isotopically Labelled Bis-(D~chlorbphosphinojmethylamine Partially Oriented in a Nematic Liquid Crystal (Colquhoun & McFarlane)Nuclear Magnetic Resonance Analysis of the Molecular Structure of FS020F: Wide Line(Allen, McCall, Aubke & Dunell) .and Infrared Spectroscopic Studies of Hidrogen Bonding' in Hindered Al'cohols.kInstance of a True Hydrogen Bonded Dinier in an Alcohol (Beclter, Tucker & Rao) .Measurement of the Small Barrier to Rotation about the Carbon-Carbon Bond29Si Studies of Aqueous Silicate Solutions (Harris & Newman) .. . . .Spectroscopy. Part 8.-Variation of the Local Diamagnetic Term in Nuclear MagneticShielding, as derived theoretically and by X-ray Photoelectron Spectroscopy: Nitrogen(Mason)Studies of the Difluoiide ion. Part 2.-D>fluorides of the' Alkaii Me'tals and AikalineStudies of the Difluoride Ion. Part 3.-Ammonium and Substituted Ammonium: .Temperatures and Pressures for (Hurle, Jones & Young) . . . .Temperatures and Pressures (Hurle, Toczylkin & Young) . . . . .Non-polar Solvent: Vibrational Spectrum of an Ion Pair in a (Schmid;) . . .in 3,5-Dichlorobenzyl Mercaptan (Schaefer & Parr) . . . . . . .Earths (Ludman, Waddington, Pang & Smith)44 SUBJECT INDEX-VOLUME 73, 1977Photochemistry of Saturated Molecules.Part 3.-Structure and Bonding in n-Alkane ExcitedStates Using INDO-Cl: Excited States and (Saatzer, Koob & Gordon).Photodissociation: Molecular Beam Studies of Ethyl Nitrite (Tuck)Rotational Energy Disposal in the Photodissociation of the Cyanogen Halides : EnergyPartitioning in (Ashfold & Simmons)Photoelectron He(1) Spectroscopic Study of Diphenyl Sulphidc, Diphenyl Sulphohe and thei;Mono- and Di-2-Pyridyl Analogues (Colonna, Distefano, Galasso, Pappalardo &Scarlata) . . . . . .of Nitrosyl Halides (Alderdice & Dixon) . . . . . ...Spectra of Allene: AngularlDistribution He&)/Ne{I) (Ling & Nyberg) . . .of the Gauche and Trans Conformers of 1,2-Dichloroethane (Gan, Peei & Whett) .(Dyke, Morris & Trickle) ..Spectroscopy: Characterization of the Ground Ionic State of the NS Molecule UsingSpectroscopy Determination of the Valence ‘E1ect;onic Configuration of Uranium Dioxideby (Evans) .* . . .Spectroscopy Study of Some Mediuni‘Size Alcohols and Hydroperoxidcs by {Ashrnore &Burgess) . . . . . . . . . .Spectrum of Dinitrogm Teiroxide: Reinterpretation of the (Gan, Peel & Willett) . .Spectrum of the PN(X%+) Molecule: Vacuum Ultraviolet (Bulgin, Dyke & Morris). .Photoexcited Chlorophyll-a with Manganese Complexes in Solution: Reactions uf (Brown,Harrjman & Porter) . . .Photolysis of Ozone: Temperature Dependence of O(”D) Formaiion in the‘ near U.V.(Moortgat, Kudszus & Warneck) . . . . . .Photon Correlation Spectroscopy : Polymer Po1idispe;sity Analysis in (King & Treadaway)Photophysical Processes in the Molecular Complexes of 1,2,4,5-tetracyanobenzene withPhotosensitized Reactions : Electron Spin Polarization (C.I.D.E.P.) in ‘(McLauchlan.Sealy &’Plane Interface with Transfer of Maker. ‘Part 2.-Non-os&lato;y and Osciliatory Modes withLinear and Exponential Concentration Profiles : Deformational Instability of a (Smensen,Hansen, Nielsen & Hennenberg) .PN(X1 1’) Molecule: Vacuum U!travio!et Ph&oelectron ‘Spectruni of the’ (Bulgin, Dike &Poisson-Boltzmann Equation for a Spherical Coiloidai Par;icle : ’Approximate AnalyticPolarisabilities and Compton Profiles for‘Solvated Eiectrons : Calculat‘ion of (U’ebster) . .Polarisation Measurements in Resonance Ranian Spectroscopy Using Linear and CircularPolarizability, Proton Transfer and Symmetry of Energy Surfaces of Carboxylic Acid-N-BasePolarizations and the Sub-millimetre Spectra in Solution of sonie Metal Acetylacetonates :Polar Mixtures. Part 4.-Comparison with Expeiimental Results for Carbon Dioxide +n-Alkane : Theoretical Prediction of Phase Behaviour at High Temperatures and Pressuresfor Non- (Hicks, Hurle & Young) .Polaron Model for the Absorption Spectrum of SolGated Electrons in Alcoiiols: Small’ (BushPoly-y-benzyl-L-glutamate using a Pseudo-random Noise Dielectric Spectromete; : DielectricPolydispersity Analysis in Photon Correlation Spectroscopy : Polymer (King & Treadaway) .Polymer Diffusion and Dimensions Moderately Concentrated Solutions (Alien, Vasudevan,Melt : Q4-Dependent Broadening in Quasierastic Incoheren; Neuiron Scatteiing from a,Polydispersity Analysis in Photon Correlation Spectroscopy (King ’& Treadaway)Polymers: Effects of Excluded Volume on the Conformation of Adsorbed (Jones & RichmondjPolynomial Matrix Method for the Calculation of a-Electron Energies for Linear ConjugatedPolymers (Kanlgud & Chitgopkar) ..Polystyrene and Its Low Molecular Analogues: Opiical Anisotiopy of (Suier & Floryj :Polystyrenes and Related Molecules : Optical Anisotropies of para-Halogenatcd (Saiz, Suter &Flory) . . . . . .Potential Energy for Tetra-alkylammonik Halides : Fa; Infrared Spectroscopic Probertiesand Interionic (Aimone, Badiali & Cachet)for the Ground State of Ammonia (Varandas & Murrellj.Vibrationally Inelastic Scattering in Collinear Systems : The Effect o*f Minima in theInteraction (Baxter & Murrell) .. . . .Powder Compacts: Permeation Time-Lag Analysis of “Anomalous” Diffusion. Part 2.-Helium and Nitrogen in Graphite (Roussis & Petropoulos) . . . . .Aromatic Donors (Craig, Rodgers & Wood) .Wit tmann) . . .Morris) . . . . . .Solution of the (White) .Polarisation Modulation Techniques : Coiiiplete (Horvath & McCaffery)46 SUBJECT INDEX-VOLUME 73, 1977PAGERaman and Luminescence Spectra of Dianthracene at High Pressures (Ebisuzaki, Taylor,Woo &Nicol) . . . . . . . . . .Raney Nickel: Alternative Explanation of the Inelastic Neutron Scattering from HydrogenAdsorbed by (Wright) ..Rare Gases with (1 1 1) Germanium Crystalplane : Interaction of (Ephraim, Calahorra & Folman)Gas Matrices. Models for the Aggregation Processes: Cluster Formation (Moskovits &Hulse) .: Observations on the Elec’tronic Spectra of CuO; Ago and AuO Isolatkd in ‘(Griffiths &Barrow) .Rate Constants of Rapid Bimolecular ‘Reaciions. ‘ Parf 5.iHydrogen Atom Reactions‘;H+N02 and H+O,: Atomic Resonance Fluorescence for (Ciyne & Monkhouse). .of Rapid Bimolecular Reactions. Part 6.-Hydrogen atom reactions: H+C12 from 300 to730 K and H+NOz at 298 K: Atomic Resonance Fluorescence for (Bemand & Clyne)Rates: Laser Fluorescence Measurements of Hg(3P0) Quenching (Phillips) .Rayleigh Bands: Truncated Series Expansion for the Correlation Function of Permanent andInduced Depolarised (Evans) .Rayleigh Scattering. Optical Anisotropyof the C-Cl Bond : Separation of ’Collision-Gducedfrom Intrinsic Molecular Depolarized (Carlson & Flory) .Reactions of Photoexcited Chlorophyll-a with Manganese Complexes in ‘Solution (Brown’,Reactivity Patterns for Hydrogen Abstraction in Alkanes Sensitized by Hg(3P;) (Marconi,Rehydration Processes on “Eta”, Theia” and “Alpha”* Aluminas I Eneigics of DifferentRelaxation Energies in X-ray Photoelectron Spectroscopy : Calculation of Adsorbatein Hydrogen-Bonded Liquids Studied’ by Dielect;ic and Keri-Effect Techniques (Ciossleyin 2-Methyl-2,4-pentanedio.l Studied by Dieiectric and ‘Kerr-effect ‘Techniques : StructuralProcesses of ReC1;- in Cubic Crystals; Luminescence Spectra (Black & Flint):Repulsion Integrals : Spin Forbidden Transitions in Some cis-CrII1A4B2 Ions.A Failure.Resonance Raman Spectroscopy Using Linear and Circular Polarisation ModulationRigid Solutions: Concentration Quenching and Excimer Formation by Perylene in (Ferreira &Rotational Energy Disposal in the Photodissociation of the Cyanogen Halides I Energy Paitition:Ruthenocene : Quenching of Triphenylene Phosphorescence in holy-(meth~lmethacrylat e ) atHarriman & Porter) . . .Orlandi, Poggi & Barigelletti) ~‘Surface (Della Gatta, Fubini & Stradella). . I .(Broughton & Perry)& Williams) . .(Crossley & Williams)of Spherical Parameterization of the Interelection (Flint, Matthews & O’Grady)Techniques: Complete Polarisation Measurements in (Horvath & McCaffery)..Porter). .. .ing in Photodissociation (Ashfold & Simons) .77 K by Ferrocene and (Vikesland & Wilkinson) . . . . .SSaturated Molecules. Part 3.-Structure and Bonding in n-Alkane Excited States UsingINDO-CI: Excited States and Photochemistry of (Saatzer, Koob & Gordon)Sb(54S3), by Time-Resolved Resonance Fluorescence : Kinetic Studies of Ground State Atoms(Hysain, Krause & Slater)Scattering and Exciton Linewidths in Naphthalene and’ Phenkthrene Molecuiar Crystals’:Phonon (Dissado & Brillante). . . .(SCF-MO) Determination of the Oxidation State of Sulphur in bis(2-carboxyphenyl) Sulphu;Dihydroxide Dilactone: Experimental (ESCA) and Theoretical (Theodorakopoulos,Csizmadia, Robb, Kucsman & Kapovits) .Self Consistent Semi-Empirical Calculation of the Electronic Band Structires of CrystallineSolids. Application to Graphite Monofluoride (Parry)Self-Diffusion in Water and Monohydric Alcohols (Pratt & WakehamjSelf-Exchange Corrected Electron Gas Model for Intermolecular Forces : Some Applicationsof a (Lloyd & Pugh)Semi-Empirical Calculation of the Electronic Band Sfructuies of Crys~alline‘Solid~. Applica:tion to Graphite Monofluoride: Self Consistent (Parry) ..Sensitized by Hg(3Po) : Reactivity Patterns for Hydrogen Abstraction in Alkanes (Marconi;Orlandi, Poggi & Barigelletti). . .Series Expansion for the Correlation Function o’f Permanent and Induced DepoiarisedRayleigh Bands : Truncated (Evans).Se2(g), SSe(g) and SeTe(g) : Determination by ;he Mass Spectrometric Knudsen Cell Methodand Discussion of the Dissociation Energies of the Molecules (Drowart & Smoes) ..Shielding, as derived theoretically and by X-ray Photoelectron Spectroscopy : NitrogenNuclear Magnetic Resonance Spectroscopy. Part 8.-Variation of the Local DiamagneticSUBJECT INDEX-VOLUME 73, 1977 47Silicate Solutions: 29Si N.M.R. Studies of Aqueous (Harris & Newman) . . . .Silicon Compounds: Ab initio Calculations Concerning Core Auger Shifts in someSimulation of a Gas-Liquid 'Surface. Part 1 : Computer (Chapela, Saville, Thompson &Rowlinson) . . . .of Surface Properties' of Ciystaliine Potassium Chloride: Mhleculk DGamics Computer(Heyes, Barber & Clarke) .. . . . .of the Liquid-Solid-Vapour Contact Angle:' Computer iSaville) . .Single Crystals and their Photochemical Significance : Structural Traps for Singlet Excitonsin Doped Anthracene (Williams & Clarke)Singlet Excitons in Doped Anthracene Single Crystals and thei; Phoiochemical Significance :Structural Traps for (Williams & Clarke).-Triplet Absorption Spectra of Some Aromatic Molecules in' Gas Matrices at 10 K (Rest;Salisbury & Sodeau) . .Small Particles of KfTCNQ- and Reiated Compounds: Optical Absorption Spec'tra o'fSolid Nitrogen Matrix: Proposed Iron-Nitrogen MoieculeProduced in a (Barrett & MontanojPhases of Benzene : Vibrational Spectroscopy at Very High Pressures.Part 18.-ThreeSolutions: Thermodynamics of MnOG CoO'and MnO $NiO iCatlow, Fender & HampsonjSolubilisation in Micelles. Part 3.-Fluorescence Polarization of Solubilisates in Cationic . .Solution: Intermolecular Energy Transfer Between Tb(thd), and Eu(thd), Complexes in(Brittain & Richardson) . . . . . . .Reactions of Photoexcited Chlorophyli-a wih Manganese Complexks in (Brown, Harriman& Porter) .Solvated Electrons: Calculatidn of Polari'sabiliiies and Compton Profiles fo; (Webster)in Alcohols: Small Polaron Model for the Absorption Spectrum of (Bush & FunabashijSolvent Spectra: Magnetic Circular Dichroism Studies of Charge-Transfer-to- (El-Kourshy &(Papavassillion & Spanou) .. .(Adams & Appleby) . . .Micelles: Absorption and Emission Studies of (Dorrance, Hunter & Philp) .Structure in Soiution'Theo;y: Role of'(Marielja, Mitchell, Ninham & Sculleyj:Vibrational Spectrum of an Ion Pair in a Non-polar (Schmidt) . .Spectral Evidence for the Existence of Green "Incipient" Dimers in Single Crystais of Anthra:Spectra of Aggregates. Part 5.-Dimers of Some Xanthene Dyes: Derivation and Interpreta-Spectroscopic Studies of Azides and Nitrenes Derived from kthracene (Alvarado, Grivei,Studies of 2,5-Dithiahex-3-yne: Struitural 'and (Beagley, Ulbrecht, Katsumata, Lloyd,Sphere and a Wall : On the van der Waals' For& between Two Spheres of a iLovejSpherical Colloidal Particle: Approximate Analytic Solution of the Poisson-BoltzrnannEquation for a (White) .Parameterization of the Interelectron Repulsion Integrals : Spin-Forbidden Transitions inSome cis-Cr111A4B2 Ions.A Failure of (Flint, Matthews & O'Grady) .Spin Distribution in Radicals Formed by Electron-loss from Phenols and from Alkyl ArilEthers: Calculation of Substituent Effects on the (Dixon, Kok & Murphy)Spin-Forbidden Transitions in Some c1'S-Cr1IIA4B2 Ions. A Failure of Spherical Parameteriz:ation of the Interelectron Repulsion Integrals (Flint, Matthews & O'Grady) .Spin Label 2,2,6,6-Tetramethyl-4-piperidinol-l-oxyl Oriented in the Inclusion Compound2'-Hydroxy-2,4,4,7,4'-Pentamethylflavan : Electron Spin Resonance Study of the (Smith& Kispert) .Spin-Lattice Relaxation' Study of Molechar Mot& in Tertiary-buiylarnmonium chloride',Bromide and Iodide: Proton (Ratcliffe & Dunell)Stability Tests: Theoretical Prediction of Phase Behaviour at High Temperatures and Pressuresfor Non-polar Mixtures.Part 1 .-Computer Solution Techniques and (Hicks & Young).Statistical Analysis of Experimental Data: The Graph-like State of Matter. Part 8.-LCGlSchemes and the (Essam, Kennedy, Gordon & Whittle)Thermodynamics of Mixed-Gas Adsorption. Localised Monolaye; Adsorption on Hetero:Treatment of Partially Mobile Adsorbates : Modified (Liklem'a)Structural and Spectroscopic Studies of 2,5-Dithiahex-3-yne (Beagley, Ulb;echt,'Katsumata;Relaxation in 2-Methyl-2,4-pentanediol Studied by Dielectri; and' Kerr:effecc TechniquesTraps for Singlet Excitons in Doped Anthracene 'Single Crystals and their PhotochemicalStructure and Bonding in n-Alkane Excited Staies Using INDO-Cl: Ekited'Statei and Photo:cene (Williams, Donati & Thomas) 8248 SUBJECT INDEX-VOLUME 73, 1977in Solution Theory: Role of Solvent (Marklja, Mitchell, Ninhani & Sculley),Mobility and Reactivity of CO; and COY Species Adsorbed on MgO: E.P.R.Siudies’ of thiof Indolyl Alkali-metal Ion Pairs in the Ground State and ;he First Excited State (Vos,MacLean & Velthorst) . .Sub-millimetre Spectra in Solution of Some ’Metai Aceiylaceionatds : Gomalbus ElectriiPolarizations and the (Haigh, Jinks, Sutton & Waddington) .Substituent Effects on the Spin Distribution in Radicals Formed by Electroniloss from Phenolsand from Alkyl Aryl Ethers: Calculation of (Dixon, Kok & Murphy) .. . .Sulphur Dioxide: Intersystem Crossing in (Ahmed, Langley & Simons)Superexchange and some Molecular Orbital Calculations of the Exchange Paramet‘er fo;Copper(11) Carboxylate Dimers (Harcourt & Martin). . .Surface Active Agent Ions, Small Molecules and Mixed Micelles : Ultrasonic Relaxation Studiesof the Exchange Process Between (Hall, Jobling, Wyn-Jones & Rassing)Part 1 : Computer Simulation of a Gas-Liquid (Chapela, Saville, Thompson &‘ Rowiinsol;)Properties of Crystalline Potassium Chloride : Molecular Dynamics Computer Simulationof (Heyes, Barber & Clarke) . . . . .Rehydration Processes on “Eta” “Theta” and “Alpha” Aluminas : Energies of DifferentStates: Simple Method for the Calculation of (Liebmak & QuimjSurfactants in the Absence and Presence of Electrolyte with a Common Counterion: Thermo:dynamics of Solutions of Interacting Aggregates by Methods Similar to Surface Thermo-Symmetric Systems: Modification of the Phase Rule for Optical Enantiomers and other (ScottiSymmetry of Energy Surfaces of Carboxylic Acid-N-Base Hydrogen Bonds Infrared .(Meriaudeau, Ben Taarit, Vedrine & Naccache) .. .. .(Della Gatta, Fubini & Stradeila) . . . . . . .dynamics. Part 3.-Solutions of Ionic (Hall) . . .Investigations: Polarizability, Proton Transfer and (Lindemann & Zundel) . .TTemperature Dependence of O(’D) Formation in the near U.V. Photolysis of Ozone (Moortgat,Kudszus & Warneck) .. . . .of the Ratio of Delayed Monomer and Delayed Excimer Fluorescence koilowing Triplet:Triplet Annihilation in Liquids: Long Range Mechanism for the (Butler & Piliing) .on Radiationless Transitions. Part 2: Effect of (Knittel, Raizdadeh, Lin & Lin)Tetracyanoethyjeiae on Potassium Chloride: LEED-AES Study of the Oriented Adsorpfion ofTheoretical Prediction of Phase Behiviou; at High Temperatures and Pressures for Non-pola;Mixtures. Part 1 .-Computcr Solution Techniques and Stability Tests (Hicks & Young)of Phase Behaviour at High Temperatures and Pressures for Non-polar Mixtures. Part 2.-of Phase Behaviour at High Temperatures and Pressures for Non-polar Mixtures. Part 3.-Comparison with Upper Critical Solution Temperatures for perfluoromethylcyclohexaneZundel, Georg ..THE SIXTH ANNUAL GENERAL MEETING OF THE FARADAY DIVISION of The ChemicalSociety was held at 9.00a.m., on 14 September 1977, in the Bernard Sunley Lecture Theatre, St.Catherine’s College, Oxford with Professor D. H. Everett, M.B.E., M.A., D.Sc., C.Chem., F.R.I.C.,in the Chair.1 MinutesThe Minutes of the Fifth Annual General Meeting of the Faraday Division, which had beencirculated previously, were taken as read and confirmed.2 Annual ReportThe Faraday Division had a successful and active year in 1976. Two General Discussions wereheld: number 61 ‘Precipitation’ was held in April in Manchester and attracted 100 participants ofwhom 40% were from overseas; and number 62 ‘Potential Energy Surfaces’ which was held atthe University of Sussex in September, when 160 persons attended including 60 from overseas.Professor D.R. Herschbach (Harvard University, U.S.A.), introduced Discussion 62 with the18th Spiers Memorial Lecture and Dr. P. J. Derrick (La Trobe University, Australia), gave the1974 Meldola Lecture on ‘The Gas-Phase Ion-Chemistry of Polyatomic Organic Molecules’ atthe meeting.Collaboration with other European Chemistry Societies was continued in 1976 when the secondjoint meeting with Deutsche Bunsen Gesellschaft, SociCtC de Chimie Physique and AssociazioneItaliana di Chimica Fisica was held in Konigstein, West Germany on ‘Energy Transfer Processesin Chemical Reactions’. Over half of the 140 participants were from outside West Germanyand the Faraday Division was well represented.In December, Faraday Symposium No. 11‘Newer Aspects of Molecular Relaxation Processes’ was held at the Royal Institution, Londonwhen 120 persons attended, a third of whom were from overseas.The Division took part in the CS Annual Congress in Glasgow in April with a meeting onMembrane Phenomena’ and in the Autumn Meeting in Sheffield with an informal discussion on‘The Chemistry of the Solid State’. The 5th International Conference on Non-Aqueous Solutions,held in July at York, was sponsored jointly with Dalton Division.Three meetings were organised by the Industrial Sub-committee : ‘Hydrogen in Metals’ at Birming-ham and ‘Aqueous Solution Properties of Synthetic Polymers’ at Cranfield Institute of Technology,both held in January and ‘Surface Analysis of Solids’ held at BP Research Centre in September.A new Subject Group for Statistical Mechanics and Thermodynamics was constituted in 1976making a total of 9 discussion groups affiliated to the Division.These groups continued to bevery active during the year and organised a number of meetings on specialist topics including:Atmospheric Chemistry (Gas Kinetics Group)Polymer Composites (Polymer Physics Group)Reference Ion-Selective Electrode Conference (Electrochemistry Group)Molecular Dynamics (Theoretical Chemistry Group)Deformation, Yield and Fracture (Polymer Physics Group)Chemisorption and Catalysis (Surface Reactivity and Catalysis Group)Present and Future Role of Neutron Scattering in Chemistry (Neutron Scattering Group)Thermal Properties of Gases and Polymers at Low Temperatures (Polymer Physics Group)Rheology of Colloids (Colloid and Interface Science Group)Electrochemical Technology (Electrochemistry Group)Theoretical Aspects of Polymer Physics (Polymer Physics Group)Neutrons and Biology (Neutron Scattering Group)Summer School-Electrochemistry (Electrochemistry Group)Summer School-Thermal Neutron Scattering (Neutron Scattering Group)Thermal Viscoelastic and Accoustical Properties of Polymers (Polymer Physics Group)Inorganic Electrochemistry (Electrochemistry Group)Statistical Mechanics and Thermodynamics of the Interfacial Region (Statistical Mechanics andMicellization (Colloid and Interface Science Group)The Practice of Gas Kinetics in an Industrial Context (Gas Kinetics Group)Preparation and Properties of Thin Films (Electrochemistry Group)Molecular Properties (Theoretical Chemistry Group)Neutron Scattering Studies of Liquid Crystals (Neutron Scattering Group)Recent Developments in Neutron Scattering Instrumentation (Neutron Scattering Group)Thermodynamics Group)5ANNUAL GENERAL MEETING 55The 1976 Bourke Lectures were given by Professor P.G. de Gennes (Colkge de France) onPolymers’ at Imperial College, London and the University of Essex and on ‘Liquid Crystals’ atthe University of Exeter. One London Symposium entitled ‘Chemical Aspects of ScatteringSpectroscopy’ was allocated to the Faraday Division which incorporated the Centenary Lectureof Dr.J. W. White (Grenoble, France).The Marlow Medal for 1976 was awarded to Dr. J. J. Burton (Exxon Corp., U.S.A.) for dis-tinguished work in nucleation and properties of microclusters.There was a small increase in the total number of members of the Faraday Division in 1976 to4402, comprising 2983 U.K. members and 1419 members from overseas.Faraday Division Newsletter No. 3 appeared in January 1976 and was distributed to U.K.members with the February issue of Chemistry in Britain and to overseas members by mail.3 Treasurer’s ReportIn the absence of the Treasurer, the financial report was presented by the President. Thefinances of the Division were reported to be healthy, 1976/7 being a year of slightly lower thanaverage commitments.A new arrangement had come into effect which permitted the Divisionto retain part of any unspent balances and this would serve the Division well in 1977/8 whenmeetings in France and The Netherlands were planned.The sums available to Organisers of the various styles of Faraday meetings, chiefly to assistoverseas contributors, had been increased in 1977/8 to:General Discussions €600Symposia €450Annual Congress E300Autumn Meeting E100.The relative magnitudes of these sums reflected the considered view of Council that GeneralDiscussions and Symposia remained top priorities for support but their absolute magnitudes were,as always, such as to permit pump-priming rather than complete support. Some enhancementwas sought for the 1977/8 budget but the Division would continue its tradition of expectingcost-effectiveness in all its activities.4 Elections to CouncilThe President commenced by formally placing on record the indebtedness of the Faraday Societyand Faraday Division to Professor F.C. Tompkins for his long service as Secretary and EditorDeep gratitude and thanks were due to him for his services over some 30 years. In 1978 ProfessorTompkins was to become President: he had been succeeded as Editor by Dr. D. A. Young on1 August 1977 and was to be succeeded as Secretary by Professor G. J. 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Thefirst, a General Discussion, to be held in The Netherlands, was jointly sponsored by the RoyalNetherlands Chemical Society and the second, to be held in France, was sponsored by theSociktC de Chimie Physique, Deutsche Bunsen Gesellschaft and the Associazione Italiana diChimica Fisica and formed the third of the biennial series of joint meetings.In addition to General Discussions and Symposia, the Faraday Division was to continue toorganise informal discussions at the Annual and Autumn Meetings of The Chemical Society andinformal meetings were also planned by the Industrial Sub-committee. Two half day LondonSymposia were sponsored by the Faraday Division in 1978 and members of the Division wereurged to support these meetings.6 Membershl'p of the DivisionIt had become apparent that some members of the former Faraday Society had not been recordedon the Chemical Society computer as members of the Faraday Division and the President remindedall members to make sure that the appropriate code was inserted on the subscription form.7 UnificationThe President reported that the Divisions had been satisfied that the unification proposals wouldnot affect adversely the academic and publishing activities of the Society and that in the proposednew statutes and byelaws, reference would be made to the Heads of Agreement between theFaraday Society and The Chemical Society which would be reaffirmedNOTICES TO AUTHORS-NO. 7/1970Deposition of Data-Supplementary Publications SchemePreambleThe growing volume of research that produces large quantities of data, the increasing facilitiesfor analysing such data mechanically, and the rising cost of printing are each making it verydifficult to publish in the Journal in the normal way the full details of the experimental datawhich become available. 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CI3Hl3NO4 requires C, 63.2; H, 5.3 %). If analytical results forcompounds which have been adequately described in the literature are to be included, they shouldbe given in the form : (Found : C, 62.95 ; H, 5.4. Calc. for C13H13N04 : C, 63.2 ; H, 5.3 %).Analyses are normally quoted to the nearest 0.05 %.6Publication of Theoretical and Computational PapersThe Primary Journals Committee has been considering future policy towards the publicationof papers with a heavily computational content, particularly where these involve standardmethods, such as semi-empirical or ab initio calculations of molecular electronic propertiesusing readily available computer programs. Many such papers report what would be con-sidered ‘routine work’ in other areas of chemistry and have often included extensive detail.A specialist sub-committee formulated a set of proposals which were circulated to a largerepresentative sample of theoretical chemists and met with general acceptance. 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Where an author considers that there is a special need to make such materialavailable to other workers, as with highly accurate computations, for example,then this may be deposited with the British Library as a Supplementary Publication.Such material should be submitted with the main paper, clearly distinguished fromit, and referred to in the main text.Guidelines can never provide sufficient criteria for acceptance or rejection of a paper.Critical assessment of the theoretical methods used in a computation, and of their suitabilityfor the purpose in hand, will continue to be entrusted to specialist referees who must alsodecide whether the results are new and advance science.6PRINTED IN GREAT BRITAIN ATTHE UNIVERSITY PRESSABERDEE

ISSN:0300-9599    

DOI:10.1039/F197773BA001

出版商:RSC    

年代:1977

数据来源: RSC

摘要:

GeneraGsed Fiirster CycleThermodynamic and Extrathermodynamic Relationships Between Proton Transfer,Electron Transfer and Electronic ExcitationBY ZBIGNIEW R. GRABOWSKI" AND WIESEAWA RUBASZEWSKAInstitute of Physical Chemistry, Polish Academy of Sciences,Kasprzaka 44, 0 1-224 Warsaw, PolandReceived 26th April, 1976The thermodynamic quantities characterizing one electron reduction, protonation and electronicexcitation, are mutually related in the ground and excited states by 6 thermodynamic (or approximatethermodynamic) cycles. The system of cycles is used to predict unknown values, and its validitymay be extended to other compounds by means of extra thermodynamic (e.g., Hammett-type)relations. Examples of known data concerning pK and pK* values of protolytic equilibria for theoxidized (Ox) and reduced (R) species are evaluated, tabulated and discussed in a search for acorrelation between the changes of pK on excitation (ApK*) and on reduction (ApK,).Both valuesare thermodynamically independent but a general common trend is empirically observed in severalgroups of systems. Some rules are derived for the excited state redox potentials and their dependenceon pH, which may be useful for photochemistry.In recent years more and more information has become available on the spectraand acid-base equilibria of free radicals,l and on protolytic equilibria in electronicallyexcited states.2 As a rule, one electron reduction causes an increase in basicity ofseveral pK units." The electronic excitation alters the electron density distributionconsiderably and often changes the pKvalues by comparable amounts ; the changeis not always an increase, numerous groups of compounds, e.g.phenols or aromaticamines, decreasing the pK dramatically on e~citation.~We have compiled the ApK values on excitation and on one-electron reductionof a few groups of organic compounds, in order to look for meaningful correlations.For the pK values, redox potentials and excitation energies, many thermodynamicor extrathermodynamic relations are known, joining any two of them. We haveattempted to combine these rules into a single system having a strong pfedictivepower. As the system is readily derived from Forster's we term it thegeneralised Forster cycle. The system of thermodynamic cycles is first defined andthen the choice of data presented.Applications of the derived systems of cycles art:shown and the system extended by extrathermodynamic relations. Finally, thesearch for correlations is discussed.1. THE THERMODYNAMIC A N D QUASI-THERMODYNAMIC CYCLESA. THREE-DIMENSIONAL GENERALISATION OF THE FdRSTER CYCLEIn fig. 1 the discussed processes are combined in a symbolic three-dimensionalform.* Throughout the paper we use the symbol pK = -log,&, where KA is the protolytic dissociationconstant of the given acid or of the acid conjugate with the given base.112 GENERALISED FORSTER CYCLEI I II I ,'II I Pnv I "nI I-, "RH I.-. I I "OrH IFIG. 1.-A cubic form symbolizing the chemical species and thermodynamic quantities in a systeminvolving one-electron transfer, one-proton transfer and electronic excitation.Explanation in thetext.Each apex of the figure represents one of the chemical entities considered, ineither its ground or excited state. The excited states and their properties are markedby an asterisk (or explicity by superscripts S , T or D for the excited singlet, tripletor doublet states, respectively), those related to the ground state have a superscriptG or are unmarked. The chemical species are symbolized by Oxz, OxHZ+l, RZ-land RH" for the oxidized base and acid forms, and for the reduced base and acidforms, respectively. Throughout the paper " reduction " and '' oxidation " meansimple one-electron transfer only; the charges often being omitted in the course ofthe paper, particularly in subscripts.A and B represent the acids (OxHZfl, RH")and bases (Ox", R*-l), respectively.Each edge of the figure represents one of the processes considered, proton transfer,electron transfer or electronic excitation ; its length should be proportional to theenergy (or free energy) change in the respective process, so that when drawn to scale,the figure becomes an irregular hexahedron, different for every system.Each face of the figure corresponds to one of the thermodynamic (or quasi-thermodynamic, i.e., approximated) cycles, are discussed below, in sections 1, B-D.FIG. 2.-The protolytic Forster cycle for the system RH f R-+ Hf.B. THE PROTOLYTIC F ~ R S T E R CYCLZThe faces of the three-dimensional figure (fig.1) lying in the plane defined by thecoordinates " excitation '' and " protonation " correspond to the well knowZ . R . GRABOWSKI A N D W. RUBASZEWSKA 13(fig. 2). The cycle, in its thermodynamically well protolytic Forster cycle 3*founded form, may be expressed bywhere AH, is the standard enthalpy change in the acid dissociation reaction,A + B+H+, in the indicated electronic state, ft is the wavenumber of the pureelectronic (0,O) transition between the ground and given excited state, for the ithchemical species, and N , h and c are universal constants. The AH, values referAHZ-AH," = Nhc(v",-Vd (1)strictly to T = 0 K but eqn (1) retains its validity to a good approximation up to300 K."For practical reasons the thermodynamic cycle after further approximations isusually applied in the form which we will describe as a quasi-thermodynamic protolyticForster cycle :ApK& = P K ~ ~ - P K ~ ~ x (v"Ox-v"OxH) hc/kT(ln 10)ApKZ = pKZ - pK: x (i& - fm) hc/kT( In 10).(24(2b)The most important approximation made in the derivation of eqn (2) is that AS,* x AS:,where AS, is the standard entropy change in the acid dissociation reaction. Theapproximation usually holds well,5 as the most important contribution to ASo, thatdue to the ionic charges, cancels between the two states.At T = 298 K the cycle can be reduced toApK* x 2.07 x 10-3Av"BA (where AYBA = VB-- VA) ( 2 4v" being expressed in cm-l.discussed el~ewhere.~Limitations on the validity of the quasi-thermodynamic Forster cycle (2) areC.THE MICHAELIS CYCLEThe faces of fig. 1 lying in the plane of '' proton transfer " and " electron transfer "are (at least for the ground state) well defined since the classical work of Michaelis.'FIG. 3.-(a) Michaelis-type redox potential against pH diagram for a one-electron redox system.(b) typical " Michaelis cycle"; AGO,, AGR are the standard free enthalpies for the reactionsHence, we have given the name '' Michaelis cycle " to the description of the changesof pK due to one-electron reduction (fig. 3)OxHz+ + OxZ + H+, and RHz + Rz- + H+, respectively.ApK," E pK,G-pKEx = ( E 2 - Eg)F/RT(ln 10)ApKT = pKg-pK& = (Ez-Eg)F/RT(ln 10)(34(3b14 GENERALISED FORSTER CYCLEwhere EB and EA are the standard redox potentials of the systems Oxz/R2-l andOxH'+'/RH", respectively.At T = 298 K this simplifies towith E measured against the standard hydrogen electrode, with European signconvention. The standard redox potentials differ by an unknown constant amountfrom the standard free enthalpy change for the process Ox" +e- + RZ-l ; they arenot measurable in condensed phases, but the differences in eqn (3) are measurableand well defined. Eqn ( 3 ) does not involve any approximations; the Michaeliscycle being an exact thermodynamic cycle.ApKe = 16.92(EA-EB)/V (34D. THE ELECTRON TRANSFER FORSTER CYCLEThe remaining faces of the three-dimensional figure (fig. I), those representing'' excitation " and electron transfer, are the least known. This is due to difficultiesin measuring the redox potentials between electronically excited species.7.Numerousattempts have been made to estimate the redox potentials of the excited species,g* l obut only a few measurements of the appearance potentials, mostly at insulator orsemiconducting electrodes,' 9 can be considered successful. Nevertheless, we canbuild a cycle (fig. 4) which we will call the electron transfer Forster cycleAH,"-AH,G = Nhc(VR-VOx). (4)o x * ... ...,.. .......... I ...... oxFIG. 4.-The thermodynamic electron-transfer Forster cycle in a " reduction " and " excitation "plane. AH, are the standard enthalpy changes for the processes of the type Oxz+' +e- + R" ;only their differences can be measured.The absolute values of the standard enthalpy changes for electron transferreactions, AHe = H i - (Hgx + I?:-), like the absolute potentials cannot be determined.As yet it is not possible to measure the difference on the left hand side of eqn (4).The approximation AS,* E AS: (where AS, is the standard entropy change forthe electron transfer reaction) is justified with limitations analogous to the case ofthe protolytic Forster cycle.4 The approximation leads to the quasi-thermodynamicrelations (5)E i - E z M (fox, - f ~ , ) N h c / FE;S - EZ % (fox- v"R)NhC/F( 5 4(5b)where P is the Faraday constant, Nhc/F = 1.24 x V cm.2. EXAMPLES OF EXPERIMENTAL ApKe AND ApK* VALUESTables 1-6 contain examples of data compiled or evaluated for the systems forwhich the most numerous and/or reliable values of pKcould be found for the oxidizedZ .R. GRABOWSKI AND W . RUBASZEWSKA 15reduced and excited species in several groups of organic compounds. Free radicalsappear either as the reduced (tables 1-4) or as the oxidized forms (table 5 and 6).The pKvalues for the stable free radicals are much more reliable than those for theshort lived species where the determination often requires additional assumptionsconcerning e.g., reaction kinetics or the assignment of transient spectra.pK* refers to the first excited singlet or doublet state of the molecules or freeradicals, respectively; pKT values for the first excited triplet state are also listed.The most reliable ApK* and pK* values are based on the protolytic Forster cycle (2)involving the (0,O) transition^,^ or on the kinetic analysis of the fluorescence quantumyield^.^ Data based only on the shifts of absorption bands are not exactly definedand indicate no more than the sign and order of magnitude of ApK*.Such inexactvalues are, as a rule, the only ones available for free radicals; all data involve atacit assumption that the given absorption band corresponds to the lowest energyelectronic transition.The ApKT values were determined either by flash photometry in buffered solutions,i.e., after the equilibrium had been attained during the lifetime of the triplet state,or from the shifts of the (0,O) transitions in phosphorescence. The last valuesusually differ from those obtained by means of T-T absorption in flash photometryby not more than a few tenths of a pH unit.4* l3The following abbreviations are used in the tables for the methods of generationof the free radicals : ph, photochemical reaction, flash photolysis ; el, electrodereactions; abbreviations for the methods of determination of pK are FO, Forstercycle (2) ; fk, fluorescence kinetics ; p, shift of the phosphorescence (0,O) bands ;TT, absorption within the triplet manifold in flash photometry.ApK* " evaluatedfrom . . . '' means " calculated from the absorption spectra reported in the referencequoted ".Unless otherwise stated, the tabulated data refer to room temperature, andaqueous, water +alcohol or H2S04 solutions. pKG values were determined byspectrophotometric methods and the free radicals generated by means of pulseradiolysis, their ApK* values being estimated from the shift of their absorptionmaxima.Negative values of pK are expressed in terms of the Hammett acidityfunction,3. APPLICATION OF THE GENERALISED FORSTER CYCLEThe system of six linear equations (2), (3) and (5) may enable evaluation of theunknown data from the 12 values characterizing the chemical system represented inOne of the most exactly investigated systems is that of N-methylphenaziniumlN-methylphenazyl radical (table 1, item 5) for which the (0,O) transitions are alsoknown :24 Gox = 20 600 em-', GOxH = 17 300 cm-l, GR = 15 900 cm-1 and fRH =13 700 cm-l ; the redox potential Eg = +0.08 V.85 These data are alreadyredundant since there are four equations [3(a), (b) and 5(a), (b)] to define threepreviously unknown values : E: = +0.62 V, Ez = + 1.07 V, Eg = +0.66 V.The values obtained in this way are presented in fig.5 in the form of a super-position of the Michaelis diagrams (E against pH) for the ground and excited states.The system is much more strongly oxidizing in the excited than in the ground state,the difference in redox potentials on excitation, E* - EG, exhibiting a distinct maximumin the range pK& < pH < pKg. Curves such as in fig. 5 can be used to predict thecourse of some photochemical electron transfer processes,fig. 116no. OxHlRH pKGl aa'b2b'c3C'd4d'ee'5f6a10.5"- 6.316 { -6.V97.615- 5.5168.815-4.321-3.524-0.33*'HC'GENERALISED FORSTER CYCLETABLE 1 .-AZA-AROMATIC COMPOUNDSApKe ApK* ApKT pK* pKYT- - 5.3;' - -11.1w+16- 15.5 - + 5*+7.71,; -w+142.2 --8.4g (+lo)"* 4.1 (5.7)%+lo(32.2") -4.724+ 6 .8 2 - + 9,2t-4.7g -10.3 --1 L Hl+H IH J+ 2r-- - -- arks*evaluated from ref.(15) and (18)*evaluated from verybroad absorptionbands ref. (1 5)*estimated with anerror of k 1.5 withsome arbitraryassumptions"evaluated from ref.(22) and (23).b' [CpH]+Z . R. GRABOWSKI AND W. RUBASZEWSKATABLE 1 .-(Contd.)17TABLE 2.-AROMATIC NITRO- AND NITROSO-COMPOUNDSOxH/RH pKG ApKe ApK* ApKT pK* pKTa - 11.329332 +5* +2;9 -6.3 -9.3 + 14.5a' 3.233,34 - - - -b -11.632 +4* - -7.6 -b' 2.935 + 5*+ 14.57.9 -- - 9.0636 +15* - 6C' 3.634.37 - - - -d 7.1638 -1329 -1.7;' -6* 5.9-9.1816 ~ + 1 3+ 2.6- - - - d' 9.837e - 4.939e' 1 1 .740 + 2"- - - -=+16- 14 -NO~H+ q?J C l DNo2:remarks*evaluated from ref.(30) and (31)*evaluated from ref.(32) (inflection point)*evaluated from ref.(3 5)*evaluated from ref.(3 6)*corrected value, thecalculatedpK* using anothervalue of pKG*evaluated from ref.(40)10 aNo2H+ HO ITNo2 e aNoH18 GENERALISED FORSTER CYCLETABLE 3.-AROMATIC CARBONYL COMPOUNDSnu. OxHiRH pKG ApKe ApK* ApKT pK* pKT remarks+7.0fk +7.6$; 12+ 1.5 *mean value from ref.+11** 5.0 (21, (411, (42) u (-6.1***evaluated from ref.(40, (431, (44)?lower limit due to themethod-+16 possible errors of 12136' 7.7j6c - 6.2*1410.0*a' 10.9;;w+10w+156.0 - *mean value from ref.(451, (46)6.9 **evaluated from ref.(47)- 4** -the equilibria may beascribed to either +4.5** +0.57 2.4 -1.5tautomer ROHi orRNH:.49*mean value of datafrom ref. (48), (49)**recalculated from ref.(49)- 1* - 6.7 - *evaluated from ref. (46)+0.2y6 + 5.4i2 - 6.0 -0.8 *mean value from ref.(411, (52)7 (54)**recalculated from ref.(52)(O# = 26 200 ~ m - l , ' ~CEO = 26 300 ~ m - l . ) ~ 'C' 9.2" - 5** - 4 - *mean value from ref.(451, ( 5 5 )(471, (55)-(58)**evaluated from ref.d -4.160 +7.7$; +10.7g1 3.6 6.69.8' 7,5 - - - - n/15 w + 1 416e - 6.85* - 2** - -4.85 - *mean value from ref.(1 6)%+16 **evaluated from ref. (62)*the reaction kineticsdata 63 are incompatiblewith pK = 6- - - -*recalculated from ref.(49) + 7.3g +2.449 y:i49 -4.9 + 8 .6 ~ ~ f { 7,34296417 %+13 - . . ~~ f ' 5.365 - 2* - 3.3 - *evaluated from ref. (65)B 4.F4 +1.8% - 6.0 -R5+8g' 126s - 1* - "evaluated from ref. (65) 11h -7.0* +11** +8.0% 4 1 *mean value from ref.18-(1 6)(43), (4.4)19 w + 1 7 **cvalua ted from ref./I' 10.5;; - 4* - 6.5 - "evaluated from ref. (47TABLE 4.-QUINONES/SEMIQUINONE RADICALS10. 0xH;RH PKG ApKe ApK* ApKT pK* pKT remarks+2* - -6 - *evaiuated from ref. (66), (67) a - 7.516 {- 8 . P20 m + 12a' 4.1' -3* - 1 - "evaluated from ref. (68)h -8.0" 45"" - - 3 - *mean value from ref. (16).(66)21 w+13 **evaluated from ref. (3 I), (66)b' 5.368.69 -2* - 3 - *evaluated from ref. (68)OH OHSome authors [e.g.ref. (8) and (86)] use the concept of redcrx potentials for systemsThey can like Ox* +e- + R which we call " mixed excitation redox potentials ".be defined asE(Ox*/R) = EZ + v",,Nhc/F (6)E(Ox/R") = EF- v",Nhc/F. (720 GENERALISED FORSTER CYCLETABLE 5.-sEMIQUINONE RADTCALS/QUINOLS AND PHENOXYL RADICAL/PHENOLNo. OxH/RH2 2232 42526aa'b6'CC'dd'ee'PHPKG AP Ke ApK*4.0" ,2**= + 69.974 -- 175 + 2*1 1.374375 - 5"77 5 + 1"+6- 3"= + 1 21374.755*368,69 - 6.6"m+8-3.8** 13.7*<7751078ba' 40-OHOH--- 1 .5g8cPK*2.0-16.3810- 1 . 39.9-PKT remarks- *mean value from ref.(70)-(72)**evaluated from ref.(701473)- *evaluated from ref. (75)- 'evaluated from ref.(74)1 *evaluated from ref. (75)- *evaluated from ref. (74)- *evaluated from ref. (76)- **evaluatedfromref. (76)*caIculated from thetau tomeric equilibriaref. (77)-4.0,, 8.5OH -OHOH@HOOH I21 2. R. GRABOWSKI AND W. RUBASZEWSKATABLE AM AMINO RADICALS1 AROMATIC AMINESno. OxH/RH pKG ApKe ApK* ApKT pK* pKT remarksa 779 +2.5* - 9.5 - *evaluated from ref. (79)a' {XX~~ - - >16'lt - *in liquid NH3, 213 K27 w +21tfrom the growth of a newemission, whereas from thedecrease of anilinefluorescence, pK* < 13**extrapolated, ref. (82)- - - - b 4.283b' 22.5 a ' w+18- -28- -c l+HExcited state redox potentials have a definite thermodynamic meaning whilemixed excitation redox potentials are usually more directly related to the reactionkinetics of excited species.87* 88 Which concept to use depends on the mechanismof the particular photochemical electron transfer reaction and will be discussed inanother paper.Taking as an example the thioninelsemithionine radical system (table 1, item 6),from the redox potentials and equilibria, one o b t a i d 8 Eg = -0.19V and EF = + 0.32 V.Substituting into eqn (6) the values for the triplet state VOx = 13 640 cm-l 890 80.6 >4 .0.40.2O ' -8 -6 - 4 ' -2 0 2 , 4 / 6 8 1 0 7P G X PK& PKG, PK R"PHFIG. 5.-Superimposed Michaelis diagrams for the redox system N-methylphenazinium ion/N-methylphenazyl free radical, for the ground and excited state and E* - EG = f(pH)22 GENERALISED FORSTER CYCLEand Toxa = 10 500 cm-l we obtain E(Ox*/R) = + 1.5 V and E(OxH*/RH) = + 1.62 V (for pH > 8.1 and pH < 6.3, respectively).These values agree well withthe quantitative results obtained for the rate of quenching of triplet thionine bydifferent reducing agent^.^For the system anthraseniiquinone radical (Ox = A'Q-, OxH = AGH)/ anthra-quinol anion (R = AQ2-, RH = AQH-), the pKG values are known (table 5, item 25)as well as EF = - 1.45 V 9 2 9 9 3 and the absorption maxima.76 In view of the useof Tmax instead of 7'' the reiiiaining 5 unknown values are defined only approximatelyby the (redundant) system of 6 linear equations (2), (3) and (5). The results areshown in fig. 6. There are two marked differences with respect to the previousexample : (i) pK* < p K G for both Ox and R (which is usual for dissociation of thephenolic OH groups), and (ii) E" < E", i.e., the system is a much stronger reductantin the excited than in the ground state.As the free radicals usually have a lowerexcitation energy than the related ( & le-) closed-shell species, this behaviour (E* < EG)will be common, in view of eqn (5), to the systems in which Ox is a free radical.I II I5, 1Q690 VRH 21510li 500 I I YoxH14 750III h~ ~ AQ"---pKG, 1 13.7 -------,A6H'0 FIG. 6.-Anthrasemiquinone radical anion (AQ- = Ox)/anthraquinol dianion (AQ2- = R) system :schematic display and its characteristics. Approximate values, evaluated from the remaining knowndata, are underlined.4. EXTENSION BY EXTRATHERMODYNAMIC RELATIONSHIPSFor numerous series of structurally related compounds some of the discussedthermodynamic data, pK, Eredox or v", are found to be approximately linear functionsof structural parameters ('' linear free energy relationships " 94* 9 5 ) .We will derivesome rules based on the Hammett " substituent constant " 97 though the scopeof these rules is much broader than the range of applicability of this kind of structuralparameter .As in most series of aromatic compounds containing a common reducible oroxidizable group, the redox potentials of aromatic ketone (or aldehyde)/ketyl radicalanion systems obey eqn (8) 9 5 * 98* 99where X = substituent, (X) and (0) denote the substituted and unsubstituted system,respectively and p is the " reaction constant ", independent of X.As a rule, theHammett equation applies to the protolytic equilibriaEB(x) -'%(o) p(EB)aX, (8)PK(X)-PKi(O) P(PK~)~,* (9Z . R . GRABOWSKI AND W . RUBASZEWSKA 23This is the case for the protonation of ketones loo (i = Ox). Assuming eqn (9) tobe valid for the ketyl radicals (i = R) we obtain a mutual correlation avoiding theexplicit use of the structural parameter(104or simplypK, z5 C,E,+C, (lob)where C , and C2 are constants for the structually related series. Eqn (lob) is thecorrelation found empirically by Hayon for a large group of carbonyl compounds ;it is shown in a corrected form in fig. 7.PKR(x) -pKR(o) a b(pKR)/P(EB)l[EB(x) -'%(0)11210< 864I , I / l , l / I I I I I I I .-2.0 -1.0 0FIG.7.-Correlation between pK$ values of the free radicals and the redox potentials Eg of thecorresponding ketone/ketyl systems, for a large variety of ketones, [see Hayon and Simic, ref. (l)].In the original paper the redox potentials referred to pH = 7. To obtain the data related to definitechemical species, we corrected the values for all ketyls with PKR > 7 : EB = E p ~ , - 0.059(pK~ - 7).The amendment improves the correlation. The points are for 1, acetone ; 2, cyclohexanone ; 3,acetaldehyde ; 4, propionaldehyde ; 5, acetophenone ; 6, formaldehyde ; 7, crotonaldehyde ; 8,p-chloroacetophenone ; 9, benzaldehyde ; 10, p-bromoacetophenone ; 11, acrolein ; 12, benzo-phenone ; 13, p-cyanoacetophenone ; 14, fluorenone ; 15, benzalacetophenone ; 16, benzil ; 17,9,lO-anthraquinone ; 18, 9,lO-anthraqujnone-1 -sulphonate ; 19, 9,l O-anthraquinone-2,6-disulpho-nate ; 20, 2-hydroxy-1,4-naphthoquinone ; 21, biacetyl ; 22, vitamin K ; 23, menaquinone ; 24,1,4-naphthoquinone ; 25, duroquinone ; 26,l ,2-naphthoquinone ; 27,2,5-dimethyl-p-benzoquinone ;28, 2-methyl-p-benzoquinone ; 29, p-benzoquinone ; 30, epinephrine ; 3 1, adrenalone ; 32, dipheno-quinone.The extrathermodynamic relations can be used to extrapolate the thermodynamic(and quasi-thermodynamic) cycles from one system to another, by a procedure whichmay be described as a projection along the chosen structural parameter. Each of thecycles, (2), (3) and (5), inter-relates four thermodynamic values. If any three of themobey an extrathermodynamic linear relationship, like (8) and (9) (i = Ox or R) inthe above example, the fourth value must obey the same kind of relationship.Inthe present example we can predict that the redox potentials for the systems protonatedketones/ketyl radicals obey eqn (1 1)where, by virtue of eqn (3a), (8) and (9), the " reaction constant "EA(x) - EA(o) p (EA) bX (1 la>(1 1b) P@A) = P ( 4 J + IP(PKR) - P(PKo,)lRT(ln lO)/F24 GENERALISED FORSTER CYCLEIf two of the thermodynamic quantities from a given cycle obey an extrathermo-dynamic linear relationship, the difference (or sum) of the other two must obey thesame type of relationship. We will demonstrate the usefulness of the rule onextrapolations of the Forster cycle (2) from one system to another.The excitation energies, 5, do not usually correlate with the Hammett-typesubstituent constants, or else the correlations are observed in a very limited range ofvariation of a.1o1 In some cases special substituent constants were suggested whichfit for the spectra-structure correlations only.'02 It is known, however, that the pK*values often obey the Hammett equation ;lo3 those for para-substituted phenolscorrelate well with the substituent constant a: .'' Taking these pK* values as internal8:2 3 4 53000rl2800 &2.m2600 742400a>.7122002 3 4 5(6)FIG. 8.-Extrathermodynamic correlations for protolytic equilibria in para-substituted phenols.(a) pKG plotted against pK* taken as an internal standard for the substituent effect, and the bestcorrelation line ; (b) (Crg - 5 ~ ) against pK*, Oi being the average of the absorption and fluorescencemaxima of the ith species.Experimental data taken from ref. (78) for the following substituentsin the para-position : (1) H ; (2) F ; (3) C1; (4) Br ; (5) CH3 ; (6) C2H5 ; (7) OCH3 ; (8) OC2H5 ;(9) SO; ; (10) N(CH3);.standard (to avoid the direct use of the 0: values) we have plotted pKG against pK*[fig. 8(a)]. A marked correlation is found (correlation coefficient Y = 0.922), wherebyAs two of the quantities (pKG and pK*) obey the same extrathermodynamic structuralcorrelation, their difference must obeyBy virtue of cycle (2) this is equivalent to the correlation of A7BA with pK* [fig. 8(b)],wherebyThe Hammett-type eqn (14) may be valid for the differences of excitation wavenumbers?B-FA,104 even if the FA and VB values taken separately do not correlate with pK* orCT+.In the present case, for para-substituted phenols, we find the following correlationcoefficients for the correlation with pK* : for CB (average from the absorption andfluorescence maxima) r = 0.563 ; for VA [(0, 0) transition approximated in the sameway] r = 0.743 ; for F,-VA [fig. 8(b)] Y = 0.904.dPKGldPK* = P(PKG)/P(PK*). (12)dApK*/dpK* w 1 -p(pKG)/p(pK*). (1 3)dA?BA/dpK* % [I -p(pKG)/p(pK*)]kT(ln lO)/hc. (142. R . GRABOWSKI AND W. RUBASZEWSKA 255 . SEARCH FOR A CORRELATION BETWEEN hpK* AND APK,Walsh pointed long ago lo5 to the analogies in effects on molecular structure ofone-electron reduction and one-electron excitation.Since his structural rules provedtheir usefulness,' O6 9 we have examined whether analogies exist between ApK*and ApK: values [for definitions see eqn (2) and (3)J The data from the tables2 to 5, related to a variety of systems, are plotted in fig. 9. For pK* only thepKs and pKD values were plotted. The ApKT values in general follow similar trendsto the ApKS values.1050 %4-5-1 00 21* El713 O8A ' 6 00140 7 8 20 2324I I I5 10 15APK,FIG. 9.-Plot of ApKgX against ApKz values for several series of compounds : 0 aromatic nitro-compounds ; 0 carbonyl compounds ; A quinones ; @ semiquinone radicals. Numbering ofthe compounds as in the tables.A very rough correlation, more a general trend, is evident.An analysis of theequations given in section 1 reveals no direct relation between ApK* and ApK, values.Extrathermodynamic relations may provide the reason since they often allow us totreat the acidic and basic species as differing in the substituent (e.g., X- for the base,XH for the acid), provided neither the electronic excitation nor the additional electronare localized on this swbstituent. The redox potentials, EZ and Eg, then follow arelation like (8). This is seldom the case for TOx and iioxH which define ApK,*, ; evenif it holds for ApK& the slope of the regression line [the " reaction constant " p ( f ) ]may be of opposite sign to p(E)lo8 (cJ: the spectra of nitrosobenzenes log).The trend observed in fig. 9 cannot be derived from this type of relationship, asthe site of proton attachment cannot be treated as a substituent, e.g., in ketones orquinones.In the series of aza-aromatic compounds this condition is not fulfilled,nor is any correlation observed for ApK* or for ApKT. Therefore the data in table 1are not shown in fig. 9.In contrast to a preliminary observation that ApK* x O.~APK,,~'O the datapresented in fig. 9 suggest something like dApK*/dApKe > 1 ; the ApK, values arealways positive and usually large, while ApK* values may be negative or positiveand undergo much larger variation with the structure of the system than do theApK, values26 GENERALISED F ~ R S T E R CYCLEnumber and precision of experimental data.The search for these correlations may become more productive with the growingThe authors are indebted to Prof.H. E. A. Kramer (Stuttgart) for the preprintsof his papers, and to a referee for his sympathetic comments and advice.E. Hayon and M. Simic, Accounts Chem. Res., 1974, 7,114.E. Vander Donckt, Progress in Reaction Kinetics, ed. G. Porter (Pergamon, Oxford, 1970),vol. 5, p. 273 ; Eldments de Photochimie Avancde, ed. P. Courtot (Hermann, Paris, 1972), p. 80.Th. Forster, Z . Elektrochem., 1950, 54,42, 531.Z. R. Grabowski and A. 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Naturforsch., 1969, 24B, 1262.8o M. Herlem and A. Thiebault, Bull. SOC. chim. France, 1970, 383.J. W. Bridges and R. T. Williams, Biochem. J., 1968, 107, 225.82 R. Stewart and D. Dolman, Canad. J. Chem., 1967, 45,925.83 P. S. Rao and E. Hayon, J. Phys. Chem., 1975, 79, 1063.84 D. W. Earls, J.R. Jones and T. G. Rumney, J.C.S. Perkin 11, 1975, 54.8 5 W. M. Clark, Oxidation-Reduction Potentials of Orgcinic Systems (Williams and Wilkins,86 L. 1. Grossweiner and A. G. Kepka, Photochem. and Photobiol., 1972, 16, 305.87 D. Rehm and A. Weller, Ber. Bunsenges. Phys. Chem., 1969, 73,834.88 E. Vogelmann and H. E. A. Kramer, Photochem. and Photobiol., in press; Z. phys. Chem.*' H. E. A. Kramer, M. Mafner and M. Zugel, Z. phys. Chem. (N.F.), 1969, 65, 276.91 E. Vogelmann, S . Schreiner, W. Rauscher and H. E. A. Kramer, Z. phys. Chem. (N.F.),92 M. E. Peover, J. Chem. Soc., 1962,4540.g3 P. Carsky, P. Hobza and R. Zahradnik, Coll. Czech. Chem. Comm., 1971, 36, 1291.94 V. A. Palm, Osnovy kolichestaennoy teorii organicheskikh reaktsii (Izdat. " Khimya ", Lenin-95 H. H. Jaffe, Chem. Rev., 1953, 53, 191.96 L. P. Hammett, Physical Organic Chemistry (McGraw-Hill, New York, 1940), p. 186.97 C. D. Johnson, The Hammett Equation (University Press, Cambridge, 1973).98 Z. R. Grabowski, Roczniki Clzem., 1954, 28, 513 ; E. T. Bartel and Z. R. Grabowski, Proc.1065.Baltimore, Md., 1960), p. 419.(N.F.), in pressH. E. A. Kramer, Z, phys. Chem. (N.F.), 1969, 66, 73.Theodor Forster Memorial Volume, in press.grad, 1967).Polarographic ConJ Warsaw 1956 (PWN, Warsaw, 1957), p. 32328 GENERALISED FORSTER CYCLE99 P. Zuman, Chem. Listy, 1954,48,94 ; Coll. Czech. Chem. Comm., 1960, 25, 3225.loo R. I. Zalewski, Bull. Acad. polon. Sci., Skr. Sci. chim., 1971, 19, 351. ' O P. Tomasik, Rdwnania poza- i para-termodynamiczne w spektroskopii absorpcyjnej w nadfioleciepolpczeh aromatycznych (Prace Naukowe Inst. Chemii i Technol. Nafty i Wegla PolitechnikiWroclawskiej, Wroclaw), in press.lo' P. Tomasik and T. M. Krygowski, Bull. Acad. polon. Sci., Sku. Sci. chim., 1974,22,443, 877 ;P. Tomasik, T. M. Krygowski and T. Chellathurai, Bull. Acad. polon. Sci., Skr. Sci. chim.,1974,22,1065.lo3 H. H. Jaff6, H. Lloyd-Jones and M. Isaks, J. Amer. Chem. Soc., 1964, 86, 2934; H. H.Jaff6 and H. Lloyd-Jones, J. Org. Chem., 1965, 30, 964.lo4 L. A. Jones and C. K. Hancock, J. Org. Chem., 1960,25,226 ; L. A. Jones and N. L. Mueller,J. Org. Chem., 1962, 27, 2356; M. Rapaport, C. K. Hancock and E. A. Meyers, J. Amer.Chem. SOC., 1961, 83, 3489.(Colloques Internat. C.N.R.S.). No. 195 ; fiditions C.N.R.S., Paris, 1971), p. 133.IoS A. D. Walsh, J. Chem. SOC., 1953, 2260 and the following series of papers.Io6 R. Hoffmann, Pure Appl. Chem., 1970,24,567 ; Aspects de la Chimie Quantique Contemporainelo' R. J. Buenker and S. D. Peyerimhoff, Chem. Rev., 1974, 74, 127.lo' Z. R. Grabowski, Zhur. fiz. Khim., 1959, 33, 728.log L. Holleck and R. Schindler, Z. Elektrochem., 1956, 60, 1142.D. Rehm and A. Weller, Israel J. Chem., 1970, 8, 259.(PAPER 6/800

ISSN:0300-9599    

DOI:10.1039/F19777300011

出版商:RSC    

年代:1977

数据来源: RSC

摘要:

Excess Enthalpies of some Binary Mixtures of 1,2-Dichloroethaneand HydrocarbonsBY B. S. MAHL* and J. R. KHURMADepartment of Chemistry-Biochemistry,Punjab Agricultural University, Ludhiana, IndiaReceived 26th April, 1976The excess enthalpies of mixtures of 1 ,Zdichloroethane with cyclohexane, benzene, toluene,0-, rn- andp-xylenes have been measured at 298.15 K. HE values for the first two systems are foundto be positive over the entire composition range whereas HE changes sign with composition in therest of the systems. Examination of the results shows that there appears to be some kind of specificinteraction between aromatic hydrocarbons and 1,2-dichloroethane.It has been established 1-9 that benzene and methylated benzenes act as weakelectron donors in the formation of intermolecular complexes with carbon tetra-chloride, chloroform and methylene chloride.In this paper we deduce the presenceof such interactions for the systems 1,2-dichloroethane +benzene, +toluene, + 0-, + m- and +p-xylenes from excess enthalpy measurements.EXPERIMENTALThe materials were purified and their purity checked as reported ear1ier.lo* l1 Excessenthalpies were measured in the previously described ~alorimeter.~ The temperature of thewater bath in which the measurements were taken was controlled to better than +O.OOl K.RESULTS AND DISCUSSIONThe excess enthalpies at different mole fractions of these systems at 298.15 Kwere fitted to the expression :where x1 and x2 are the mole fractions of the components 1 and 2 in the mixture.HE/x1x2 = ho+hl(xl-x2)+h2(x1 - x ~ ) ~ + ~ ~ ( x ~ - x ~ ) ~ (1)TABLE l.-VALUES OF THE CONSTANTS OF EQN (1) AT 298.15 Ksystem ho/J mol-1 hl/J mol-1 h l / J mol-1 h3/J mol-1 aHE/J mol-11,2-dichIoroethane+1 ,Zdichloroethane+1 ,Zdichloroethane+1,2-dichIoroethane+1 ,Zdichloroethane +1 ,Zdichloroethane+benzene 260.5 229.0 167.4 - 44.7 1.4toluene - 107.5 415.1 276.1 22.0 3.9o-xylene - 77.2 702.3 232.1 - 155.2 1.5rn-xylene 60.3 901.6 292.4 - 239.2 2.6p-xylene - 258.2 658.6 399.1 21 3.2 4.2c yclo hexane 5552.9 121.6 425.5 223.9 4.1230 EXCESS ENTHALPIES OF BINARY MIXTURESThe coefficients ho, h l , h2 and h3 for each mixture, evaluated by fitting the experi-mental values of HE/x1x2 to eqn (1) by the method of least squares, are recorded intable 1, together with the estimated standard deviation a(HE) calculated from theequationwhere the sum is taken over the set of n(observed) results and rn is the number ofcoefficients.The values of HE are reproducible to within 4.0 J mol-1 and are plottedin fig. (1)-(6).O W E ) = [ W O E b s - ~cEalc)2/(~,,s - m)l+iaoo12001200no01000r( 900800?OOw 600 ' 500LOOI -230020010002 OL 0 6 08 10XIFIG. 1 .-Enthalpies of mixing HE against molefraction x1 of 1,2-dichloroethane (1) + cyclo-hexane (2)x1FIG. 3.-Enthalpies of mixing HE againstmole fraction x1 of 1,2-dichloroethane (l)+toluene (2).x1FIG. 2.-Enthalpies of mixing H E againstmole fraction xi of 1 ,Zdichloroethane (1) +benzene (2).0 2 OL 0 6 08 1 0X1FIG. 4.-Enthalpies of mixing HE againstmole fraction x1 of 1,Zdichioroethane (I)+o-xylene (2)B.S. MAHL AND J . R. KHURMA 31The HE values of 1,2-dichloroethane +benzene and 1,2-dichIoroethane + cyclo-hexane are positive over the whole range of composition whereas for 1 ,Zdichloro-ethane + toluene, + u-, + m- and +p-xylenes, HE values change sign with composition.In the case of 1 ,2-dichloroethane + benzene, HE is a maximum at a mole fraction of1,2-dichloroethane of - 0.7. The excess heat is thus markedly asymmetrical inthese systems except for I ,Zdichloroethane + cyclohexane where it is symmetrical.Such asymmetry is common in mixtures in which specific interactions occur.126050LO3020104I 10 2 -2032 -302 -Low- 50-60-70-60-90-1 no0 2 O L 0 6 0 8 1 0x1FIG.5.-Enthalpies of mixing HE againstmole fraction xl of 1,Zdichloroethane (1)+p-xylene (2).1101009080706050t LO0M -E 3o2 20z ' 0w-50 "?.i -10I L 1 ' 1 ' 1 ' " 102 o c 06 o a 1 0X1FIG. 6.-Enthalpies of mixing H E againstmole fraction x1 of 1,2-dichloroethane (1)+m-xylene (2).HE values are smaller with benzene than with cyclohexane and are smaller stilland even change sign with toluene and the xylenes as a function of composition.The sharp decrease of HE values of 1,Zdichloroethane with benzene, as comparedwith that with cyclohexane although their sizes are approximately the same, and theexothermic mixing with toluene and xylenes at low mole fractions of 1,2-dichloro-ethane provide strong evidence for the existence of specific interactions in thesesystems.This is further supported by the positive temperature coefficient of excessvolumes of mixing l3 of these systems.It is, however, difficult to comment specifically about the nature of these inter-actions from thermodynamic evidence alone. A weak complex formation l4 betweenthe n-electrons of the various aromatic hydrocarbons under the present investigationwith 1 ,Zdichloroethane could be a probable explanation for the results obtained.W. G. Schneider, J. Phys. Chem., 1962, 66,2653.C. J. Creswell and A. L. Allred, J. Phys. Chem., 1962, 66, 1469.R. P. Rastogi, J. Nath and R. R. Misra, J. Chem. Thermodynamics, 1971, 3, 307.M. L. McGlashan, D. Stubley and H. Watts, J. Chem. Soc. (A), 1969, 673.J. R. Goates, R. J. Sullivan and J. B. Ott, J. Phys. Chem., 1959, 63, 589.R. K. Nigani and B. S. Mahl, Indian J. Chem., 1972, 10, 1167. ' R. K. Nigam and B. S. Mahl, J.C.S. Faraday I, 1972, 68, 1508.a L. W. Reeves and W. G. Schneider, Canad. J. Chem., 1957, 35, 25132 EXCESS ENTHALPIES OF BINARY MIXTURESN. C. Perrins and J. P. Simona, Trans. Firaday Soc., 1969, 65, 390.3, 363.loB. S. Mahl, R. K. Nigam, S. L. Chopra and P. P. Singh, J. Chem. Thermodynamics, 1971,l1 J. N. Vij and B. S. Mahl, Thermochim. Acta, 1975, 12, 155.l2 J. S. Rowlinson, Liquids and Liquid Mixtures (Butterworth, London, 1969).l3 M. S. Dhillon, J. Chem. Thermodynamics, 1974, 6, 1107.l4 L. A. K. Staveley, W. I. Tupman and K. R. Hart, Trans. Faraday SOC., 1955, 51, 323.(PAPER 6/802

ISSN:0300-9599    

DOI:10.1039/F19777300029

出版商:RSC    

年代:1977

数据来源: RSC

摘要:

Sorption of Water Vapour by some Derivativesof Bovine Serum AlbuminBY COLIN H. ROCHESTER* AND A. VALERIE WESTERMANChemistry Department, The University, Nottingham NG7 2RDReceived 12th May, 1976Isotherms for the sorption of water vapour by succinyl, acetyl, amidino, methyl and carbodiimidederivatives of bovine serum albumin at 298 K have been determined gravimetrically. The effects ofthe specific chemical modifications on the uptake of water by B.S.A. are discussed by considerationof the groups in the protein which are possible sites for water sorption. Adsorption onto both sidechain polar or ionic groups and main chain peptide groups occurs. Release of main chain peptidegroups from the a-helical conformation enhances their capacity to sorb water.A study of the sorption of water vapour by five samples of bovine serum albuminisolated at different pH values in the range 2.0-10.2 has suggested that the sequenceCOO- > NH; > NH2 > COOH reflects the relative amounts of water sorbed at aparticular relative vapour pressure by the side chain groups in B.S.A.I The existenceof -COO-.+H3N- intermolecular salt bridges in the " dried " native proteindecreased water uptake.Water was also sorbed onto main chain peptide groupsparticularly when the latter were not involved in the hydrogen bonding interactionswhich lead to a-helical structure. The present paper reports a further attempt toseparate the effects of side chain groups, peptide bonds and structure on the sorptionof water by B.S.A. A series of chemically modified derivatives of B.S.A.have beenprepared and their interactions with water have been studied gravimetrically.EXPERIMENTALThe preparation of chemically modified derivatives of B.S.A. (source as before)' wasfollowed by dialysis against deionized water and freeze drying in a Chemistry LaboratoryInstrument SB4 freeze dryer. The products were stored over phosphorus pentoxide at273 K. Preparation details were as follows.SUCCINYLATED B . s . A . ~B.S.A. (10 g) was dissolved in water (500 cm3) and the pH was adjusted to 7.5 by additionof aqueous NaOH solution (0.2 mol dm-3). Succinic anhydride (25 g) was added in aliquotsover 2 h. The pH was maintained at 7.5 throughout the experiment by addition of aqueoussodium hydroxide (5 mol dm-3).The product is referred to as succinylated B.S.A. I. Fourother succinyl derivatives of B.S.A. were prepared by a similar procedure but with differingratios of B.S.A. to succinic anhydride as follows :mol anhydride/derivative mol lysinesuccinylated B.S.A. I 26.7succinylated B.S.A. IT 26.7succinylated B.S.A. IV 4.0succinylated B.S.A. I11 12.0succinylated B.S.A. V 1 .o1-2 33weight of weight of succinicB.S.A.lg anhydridejg10 25.05. 12.55 5.615 1.875 0.4634 WATER-I-B.S.A. DERIVATIVESACETYLATED B.S.A.3B.S.A. (10 g) in water (300 cm3) was cooled to 277 K and the pH adjusted to 7.5 by theaddition of aqueous sodium hydroxide (1 rnol dm-3). Acetic anhydride was added sIowIyover 2 h and the pH maintained at 7.5 with aqueous sodium hydroxide (1 rnol dm-3).AMID IN ATE D B.S.A.4B.S.A.(5 g) in water (500 cm3) was cooled to 273 K and the pH was adjusted to 8.3 withaqueous sodium hydroxide (5 rnol dm-3). Ethyl acetimidate (80 g) was added over 2 h thepH being kept within the range 8.3-8.6 with aqueous sodium hydroxide (5 rnol dm-3).Owing to its instability ethyl acetimidate was prepared immediately before use.METHANOL ESTERIFIED B.s.A.~B.S.A. (10 g) was stirred at room temperature for 3 weeks with a mixture of methanol(1 dm3) and aqueous hydrochloric acid (10 cm3, 35 % wlv). The solid product was separatedby filtration, washed with ether, dried and slurried with water (400 cm3) and the pH of thesolution adjusted to 6.0 by addition of aqueous sodium hydroxide (2 rnol dm-3).Theresulting derivative of B.S.A. after dialysis and freeze drying is referred to as methanolesterified B.S.A. I. Three further derivatives were prepared by altering the concentration ofcatalyst and time of reaction as follows :concentration of time ofderivative HCl catalyst/mol cm-3 reactionlweekmethanol esterified B.S.A. I 0.10 3methanol esterified B.S.A. I1 0.15 1methanol esterified B.S.A. I11 0.15 3methanol esterified B.S.A. IV 0.15 4CARBODIIMIDE DERIVATIVE OF B.S.A?Ethylene diamine (15 g) was added slowly to B.S.A. (5 g) in water (250 cm3) followed byethyl dimethylaminopropyl carbodiimide hydrochloride (5 g). The pH was kept at 4.7 withaqueous hydrochloric acid (3 rnol dmW3). The reaction was stopped after 2% h by theaddition of an equimolar mixture (I rnol dm-3) of aqueous sodium acetate and acetic acidat pH 4.7.HYDROXY-ACETYLATED B.s.A.*Acetic anhydride (6.7 cm3) was added to B.S.A.(5 g) in trifluoroacetic acid (70 cm3) at273 K and after 20 min the solution was poured into ice cold water. The precipitate waswashed with acetone (3 x 150 cm3) and ether (3 x 150 cm3), dried in vacuo and suspended inwater (300 c1n3). The pH of the solution was adjusted to 7.0 with aqueous sodium hydroxide(2 rnol dm-3).The a-helix, sodium ion and chloride ion contents of the B.S.A. derivatives were deter-mined as b e f ~ r e . ~ During the chloride analyses some of the derivatives gave a precipitateafter addition of the ferric alum and mercuric thiocyanate solutions. The precipitates wereremoved by centrifugation for 10 min.The extents to which B.S.A.had been modified during the preparation of derivatives wereestimated by n.m.r. analysis of hydrolysates of the derivatives.21 The n.m.r. spectrum ofB.S.A. in water consists of broad bands. The modified proteins were, therefore, firsthydrolysed because it was known that hydrolysis would decrease band widths and thusfacilitate analysis and interpretation of the relevant band positions and intensities. Thederivatives (1 g) were hydrolysed by refluxing (3 h) with concentrated aqueous HCI (6 cm3).Spectra were recorded with a Varian HA-100 spectrometer locked onto the water signal asthe reference standard. The analysis of the spectra is exemplified by the results for hydro-lysed B.S.A.and hydrolysed acetylated B.S.A. (fig. 1). The bands between 8.82 and 9.77may be assigned to the methyl groups of leucine, isoleucine, and valine, and are sufficientlC. H. ROCHESTER AND A. V. WESTERMAN 35well resolved from the rest of the spectrum to act as an internal intensity standard. Thereare 0.1911 mol of leucine, isoleucine and valine per mole of residues in B.S.A. Each aminoacid has six methyl H-atoms and, therefore, the intensity of the band between 8.8 z and 9.7 zwill be equivalent to 1.15 H-atoms per residue in B.S.A. Comparison of the spectra in fig. 1shows increases in absorption intensity between 6 2 and 72 in the spectrum of acetylatedB.S.A. due to the appearance of bands which may be assigned to H-atoms in acetyl groups.7FIG.1 .-N.m.r. spectra of (a) hydrolysed B.S.A. and (b) hydrolysed acetylated B.S.A.Measurement of the integrated intensities IA, IB, Ic, and ID in regions A, B, C and D re-spectively of the spectra (see fig. 1) enabled calculation [eqn (l)] of A1 the increase in intensityof bands due to the presence of acetyl groups.Hence the number of moles of acetylated residues per mole of total residues in B.S.A. wasgiven by (AI/3)(1.15/IB).The uptake of water vapour by the B.S.A. derivatives at 298 K was determined gravi-metrically as bef01-e.~A1 = Ic- IA(IDIIB). (1)RESULTSDetails of the characterization of the derivatives of B.S.A. are given in table 1.Molecular weights of the products were estimated as b e f ~ r e . ~ The modifications toB.S.A.which were carried out were chosen because of their specificity towards certainside chain functional groups. The extents of reaction are, therefore, quoted withrespect to the particular amino acid residues whose side chain groups were beingmodified. The number of residues of each amino acid in one molecule of B.S.A.was evaluated from the data of Spahr and Edsall lo and a molecular weight of 66 000for unmodified B.S.A.I36 WATER+ B.S.A. DERIVATIVESTABLE DETAILS OF THE CHARACTERIZATION OF THE DERIVATIVES OF B.S.A. THE QUOTEDSODIUM AND CHLORIDE CONTENTS ARE THE NUMBER OF IONS PER MOLECULE OF PROTEINB.S.A. derivative residues modified?bovine serum albumin -succinylated B.S.A. I 100 % Lys70 % Tyrsuccinylated B.S.A. I1 100 % Lys100 % Tyrsuccinylated B.S.A.111 100 % Lys70 % Tyrsuccinylated B.S.A. IV 95 % Lyssuccinylated B.S.A. V 20 % Lysacetylated B.S.A. 100 % Lys100 % Tyramidinated B.S.A. 85 % Lysmethanol esterified B.S.A. Imethanol esterified B.S.A. 11methanol esterified B.S.A. 111methanol esterified B.S.A. IVcarbodi-imidederivative of B.S.A.hydroxy-acetylated B. S. A.22 % Asp+ Glu16 % Asp+Glu3 1 % Asp+ Glu31 % Asp+Glu78 % Asp+ Glu15 % Ser+Thr100 % Tyrt f. -2 :<.Nafcontent7137731161013044105343111c1-content0000000003750521160molecularweight66 00075 30076 00075 30073 20067 40071 30068 50069 00068 80069 00069 10074 30067 500% helicalcontent54113214175331511922201616i** Not sufficiently soluble for O.R.D.analysis.The equilibrium uptake of water by the B.S.A. derivatives as a function of therelative vapour pressure of water (Po = 3159.5 N m-2 at 298 K) is given in table 2.The percentage regain equals one hundred times the weight of water sorbed dividedby the weight of “ d r y ” protein. The data are also converted to the number ofwater molecules sorbed per molecule of protein.TABLE 2.-GRAVIMETRIC DATA FOR THE SORPTION OF WATER VAPOUR BY B.S.A. AND THIRTEENDERIVATIVES OF B.S.A. AT 298 KR.V.P. %regain -ELFEZ, mol protein R.V.P. %regain -ELEE- R.V.P. %regain mol protein mol protein(a) succinylated B.S.A. I0.026 1.75 730.060 3.41 1430.148 5.31 2220.181 5.96 2490.278 7.71 3230.353 9.26 3870.516 15.09 63 10.628 19.37 8100.709 24.56 10270.774 32.10 13430.843 46.94 19640.928 71.90 3008(b) succinylated B.S.A. I10.051 1.09 460.082 1.97 830.091 2.33 980.196 4.63 1960.395 7.22 3050.499 9.74 4120.665 13.28 5610.730 15.74 6650.829 20.51 8660.903 24.84 10490.977 45.40 1917(c) succinylated B.S.A.1110.030 1.88 790.098 4.31 1800.156 5.35 2240.288 8.39 3510.428 12.04 5040.601 17.23 7210.700 20.84 8720.737 25.26 10570.788 29.84 12480.839 35.42 14820.944 63.80 266C. H. ROCHESTER AND A. V. WESTERMAN 37TABLE 2.-contd.R.V.P. %regain -EELEEL mol protein(d) succinylated B.S.A. IV0.019 1.29 530.048 2.46 1000.072 3.47 1410.099 4.42 1800.205 6.12 2490.351 8.81 3580.431 11.28 4590.575 15.30 6220.646 18.87 7670.726 22.41 91 10.762 23.82 9690.789 27.08 11010.816 29.35 11930.942 56.57 2296(9) amidinated B.S.A.0.065 3.06 1240.106 4.07 1550.214 6.28 2390.307 6.73 2560.404 8.36 3180.474 10.32 3930.601 12.57 4780.690 13.78 5240.755 16.91 6440.816 23.58 8970.884 27.64 1052( j ) methanol esterified0.0230.0570.1210.1650.2960.3870.4880.5420.5800.6570.7780.8340.8500.8750.9080.942B.S.A. I111.44 552.18 842.80 1073.53 1355.67 2176.50 2498.80 3379.63 3 6910.53 40412.54 48116.00 61318.65 71 520.27 77723.78 91228.40 108931.50 1208(m) hydroxy-acetylated B.S.A.0.017 0.94 350.052 2.19 820.093 3.33 1250.194 4.86 1820.319 6.74 253R.V.P.%regain mol protein(e) succ0.0500.0960.1690.3090.4590.5640.6520.7040.7580.8310.8810.952:inylated B.S.A. V1.07 402.64 993.73 1406.69 2519.54 35712.41 46515.28 57217.50 65519.86 74422.54 84425.92 97147.36 1773(h) methanol esterified0.072 1.87 720.101 2.85 1090.209 4.51 1730.279 5.64 2160.456 7.89 3020.467 8.44 3240.638 12.02 4610.711 14.08 5400.848 19.54 7490.870 22.04 8450.885 23.28 8920.952 28.52 1093B.S.A. I(k) methanol esterified0.0370.0800.1290.1840.2980.4070.4590.6180.7170.7930.8670.9390.9640.3770.5240.6380.6930.816B.S.A. IV1.36 522.38 913.45 1324.28 1 645.59 2157.30 2808.58 32910.89 41812.82 49215.51 59518.91 72622.60 86828.93 11127.87 29510.99 41212.84 48214.75 55318.92 710R.V.P.%regain - mol protein(f) acetylated B.S.A.0.026 1.59 630.056 2.85 1130.146 4.44 1760.257 6.30 2500.333 7.30 2890.411 9.42 3730.556 11.78 4670.663 14.76 5850.788 19.75 7820.894 28.95 11470.942 36.70 1454(i) methanol esteB.S.A. I10.046 1.760.090 3.580.219 5.320.323 6.560.407 8.160.530 10.720.611 12.560.698 14.650.785 17.600.825 20.480.884 23.630.898 26.580.919 29.98:rified6713720325 131241048056067378390310161146(I) carbodi-imide derivative of0.0210.0530.1270.1440.2290.3340.4370.5270.6010.7330.8270.9380.8190.8780.9100.943B.S.A.1.28 532.88 1194.04 1674.69 1945.69 2357.50 3109.57 39511.78 48614.62 60418.72 77325.21 104146.08 190319.19 72021.74 81524.18 90727.63 10338 WATER -k B.S.A.D ERI VAT1 VESDISCUSSIONMETHANOL ESTERIFIED B.S.A.Brodersen et aE.I2 reported that methylation of the carboxyl side chain groups ofhuman serum albumin had little effect on the extent of water uptake by the protein,and concluded that water was sorbed through interactions with main chain peptidegroups rather than with polar side chains. In contrast, Watt and Leeder found thatmethylation of keratin decreased water uptake, as would be expected if water sorption,at least in part, involves interactions between water molecules and specific polar sidechain groups in the protein. In the present work methylation of B.S.A.also causeddecreases in water uptake for all four methanol esterified derivatives over the entirerange of relative vapour pressure which was studied. The isotherms for two of thederivatives are compared with that for B.S.A. in fig. 2. The isotherms for the othertwo derivatives were similar but are omitted from the figure for clarity.Trelative vapour pressureFIG. 2.-Isotherms for the sorption of water vapour by (a) B.S.A.l, (b) methanol esterified B.S.A. 11,and (c) methanol esterified B.S.A. IV, at 298 M.The four methanol esterified derivatives of B. S. A. had similar a-helical contentswhich were appreciably less than the a-helical content of the unmodified protein(table 1). The release of main chain peptide groups from the a-helical conformationshould lead to an increase in water uptake l4 if sorption by the peptide groups wasthe predominant influence on the water sorption isotherm.This is the reverse of theexperimental result. The decrease in water uptake observed must be primarily dueto the replacement of charged -COO- side chain groups in the glutamic and asparticacid residues by uncharged -COOMe groups. Measurements of isotherms for thesorption of water by sodium poly-L-glutamate and by methanol esterified poly-L-glutamic acid have shown that the uptake of water by -COO- groups is much greateC. H. ROCHESTER AND A. V. WESTERMAN 39than that by -COOMe groups over the entire water vapour pressure range.9Detailed comparison of the results for B.S.A. and for the poly-L-glutamic acidderivatives shows that the decreases in water uptake per side chain group modified inpassing from B.S.A.to methanol esterified B.S.A. were similar in magnitude to thecorresponding decreases in passing from sodium poly-L-glutamate to methanol-esterified poly-L-glutamic acid. It must be concluded as before 1 9 that the inter-action between water and ionic or polar side chain groups in proteins has a majorinfluence on the total water sorption isotherm.CARBODIIMIDE DERIVATIVE OF B.S.A.The carbodiimide modification of B.S. A. using ethylene diamine as reagentresulted in the conversion of carboxyl side chain groups to -CO . NH . CH,CH,NHigroups which contain both a peptide group and a protonated amino group.' Anappreciable loss of a-helical structure also occurred.The replacement of one ionicside chain group by another, the release of main chain peptide groups from the helicalconformation, and the generation of side chain peptide groups, would probably beexpected to lead to the increase in water uptake which is observed (fig. 3) providingwater sorption onto both side chain and main chain peptide groups contributed to theoverall isotherm. Previous studies of water sorption by polypeptides and by B.S.A.derivatives have shown that side chain -NHZ groups do not adsorb as much waterat a given vapour pressure as do -COO- groups. The increased uptake of water byrelative vapour pressureFIG. 3.-Isotherms for the sorption of water vapour by (a) carbodiimide derivative of B.S.A., (b) 0acetylated B.S.A., 0 B.S.A., and (c) hydroxy-acetylated B.S.A., at 298 K40 WATER+B.S.A.DERIVATIVESthe carbodiimide derivative of B.S.A. may have arisen because the high extent ofmodification led to an increase in the total number of ionic sites as a result of thedisruption of intramolecular -COO-. +H3N- salt bridges. However, it is morelikely that the predominant influence arises from the generation of side-chain peptidegroups which, as before, act as adsorption sites contributing appreciably to theisotherm particularly at moderate and high humidities. It would be illogical tosuggest that side chain peptide groups act as adsorption sites, whereas those mainchain peptide groups which are not involved in any intramolecular hydrogen bondinginteractions do not.Adsorption of water onto main chain peptide groups, particularlyisolated peptide groups,14 must, therefore, contribute to the overall uptake of waterby proteins.HYDROXY-ACETYLATED B.S.A.Acetylation of all the tyrosine residues and 15 % of the serine and threonineresidues in B.S.A. led to a decrease in the uptake of water by the protein at all vapourpressures (fig. 3) and a product which was insoluble in water. The O.R.D. spectrumof the derivative could not, therefore, be determined and its a-helical content isunknown. However, comparison of the isotherms [fig. 3(b) and 3(c)] suggests thatside chain acetate groups in hydroxy-acetylated B. S. A. are weaker sorption sites thanthe corresponding unmodified hydroxy-groups in B.S.A.Interactions between waterand side chain hydroxy-groups must contribute to the overall isotherm for thesorption of water by the protein. Adsorption of water onto both aliphatic (serine andthreonine) and aromatic (tyrosine) hydroxy-groups has previously been characterizedby analogous studies involving keratin l 5 to those described here involving B.S.A.The results from the two studies are similar.concluded that at 50 % relative humidity each aliphatic and aromatic hydroxy-groupin keratin was associated on average with 0.34 and 1.0 water molecules respectively.The loss of all the tyrosine OH-groups and 15 % of the serine + threonine OH-groupsfrom B.S.A. would be expected, if these figures were applicable for B.S.A. as well askeratin, to give a decrease in water uptake of 23 molecules per molecule of protein.The experimental isotherms [fig.3(b) and (c)] differed by 27 molecules of water permolecule of protein. This comparison can only be qualitative, as it is a gross over-simplification, but it does show that there is a measure of agreement, at least up tomoderate humidities, between the present results for B.S.A. and previous data forkeratin.15 At high humidities the decrease in water uptake caused by the hydroxy-acetylation of B.S.A. was considerably greater than the losses caused by modificationof the hydroxy-groups in keratin. Perhaps in B.S.A. the presence of side chainhydroxy-groups promotes the build up of aggregates of water molecules at high vayourpressures of water.For example, Watt and LeederA MIDI N ATE D B.S.A.The amidination reaction4 led to 85 % replacement of the -NH2 groups oflysine residues by -NH .C(=NH)CH3 groups which are more strongly basic.16The helical, sodium and chloride contents of the product were similar to those for theunmodified protein. The slightly increased uptake of water at low vapour pressures(fig. 4) suggests that the primary adsorption of water onto -NH.C(=NH,+)CH,sites is more favourable than adsorption onto -NH; groups. At moderate vapourpressures the effect was reversed by up to a maximum decrease in water uptake at70 % relative humidity of - 1.3 water molecules per lysine residue modified. Thismight have arisen because the tetrahedral structure of the -NHZ ionic group waC.H. ROCHESTER A N D A. V. WESTERMAN 41more likely than the planar structure of the =NHZ group to favour the build up ofaggregates of water molecules around the ionic sites.3relative vapour pressureFIG. 4.-Isotherms for the sorption of water vapour by (a) B.S.A. and (6) amidinated B.S.A., at 298 K.ACETYLATED B.S.A.N.m.r. spectra of the hydrolysate of acetylated B.S.A. showed that the acetylationreaction had produced both N-acetylated lysine and 0-acetyl tyrosine in 100 % yield.Some di-acetylated lysine or 0-acetylated serine and threonine were probably alsoformed. The 44 sodium ions present in acetylated B.S.A. balanced the charge ofionized carboxylic acid groups. Despite the high extent of modification produced bythe acetylation reaction the water sorption isotherm for acetylated B.S.A.was identicalto that for B.S.A. over the entire water vapour pressure range (fig. 3).Brodersen et a1.12 found that acetylated and unmodified human serum albumingave similar water sorption isotherms, and concluded that water was bound to mainchain peptide groups rather than to polar side chain groups in the protein. However,water uptake by proteins was decreased by acetylation of collagen,17 silk fibroinand keratin l 3 and by benzoylation of casein.18 The decreases have been ascribedto changes involving hydration of the main polypeptide chain1' or of side chaingroups. 3 9 A study of water sorption by poly-L-lysine, poly-L-lysine hydrobromideand acetylated poly-L-lysine showed that side chain -NH .CO . CH3 groups interactless strongly than either -NH2 or -NH: groups with water.g However, atmoderate and high vapour pressures appreciable adsorption of water occurred ontoboth main chain and side chain peptide groups in acetylated poly-L-lysine. Thepresent results for B.S.A. probably arise because of several opposing effects. Theacetylation of tyrosine side chain hydroxy-groups decreases the uptake of water at allvapour pressures [fig. 3(c)]. Replacement of -NH, or -NHi groups (the latter arezwitterionic with --COO- groups in the dry protein) with -NH. CO. CH3 groupsshould decrease water sorption at low hun~idities,~ The elimination of -NH2 group42 WATER-I-B.S.A. DERIVATIVESwill also prevent zwitterionic interactions between -NH2 and --COOH groups and,therefore, give a decrease in water uptake due to the conversion of some -COO- to-COOH groups. This effect will be opposed by the presence of 44 sodium ionswhich balance the charge of 44 -COO- groups in acetylated B.S.A.Also-COO-.+H3N- salt bridges 19* 2o will be destroyed to give two hydrophilic sidechain sites, -NIP. CQ . CH3 and -COOH (or -COO-). The loss of helical content(table 1) caused by acetylation generates isolated main chain peptide groups l4 whichcan act as sites for water sorption particularly at moderate and high vapour pre~sures.~Thus, although the result for acetylated B.S.A. is apparently simple, there is ampleevidence l* that the explanation is probably complex. To discuss the result solelyin terms of water-protein interactions involving main chain peptide groups is in-adequate.Adsorption of water at both side and main chain groups must occur if theisotherm is to be satisfactorily rationalized.SUCCINYLATED B.S.A.The isotherms for the five succinylated derivatives of B.S.A. also require explana-tions involving several effects. Two derivatives (11, V) sorbed less, or about the sameamounts, of water than B.S.A. whereas three derivatives (I, 111, IV) sorbed more waterover the entire vapour pressure range. Some crossing of isotherms occurred as therelative abilities of the derivatives to sorb water differed slightly at low, moderate andhigh humidities. A detailed discussion of the results is unnecessary as it would onlyreiterate at length concepts which have already been presented in this and previousdiscussions.' 9 However, certain general implications of the data are worth noting.Succinylation resulted in the conversion of side chain -NH2 to-NH. CO.CHZCHZCOOHgroups (or their charged counterparts) and of tyrosine aromatic hydroxy-groups to-0. CQ . CH2CH2COOH groups. The relative abilities of the derivatives to sorbwater gave no obvious correlation with the numbers of lysine or tyrosine side chaingroups which had been modified. However, correlations were observed betweenwater uptake and both the sodium ion contents and the a-helix contents of the succinylcompounds. The relative amounts of water sorbed by the compounds were in thesequences I > I11 > IV > I1 > V at low humidities, Z 21 111 > IV > I1 V atmoderate humidities, and I > I11 > IV > V > I1 at high humidities.The sodiumcontents were in the similar sequence I > I11 > IV > I1 > V whereas the a-helicalcontents were the exact reverse I < 111 < IV < I1 < V. The isotherms, therefore,give further support for the conclusions 1* that side-chain charged carboxyl groupsconstitute strong adsorption sites for water and that water sorption is also enhancedby the loss of helical content in a protein. Main chain peptide groups constitutewater-sorption sites particularly when they are not involved in intramolecular hydrogenbonding interactions. l 4The authors thank the S.R.C. and Unilever Ltd for financial assistance andDr. B. Rossall for helpful discussions.C. H. Rochester and A. V. Westerman, J.C.S. Faraday I, 1976, 72,2498.I. M. Klotz, Methods EnzyrnoL, 1967, 11, 576.J. F. Riordan and B. L. Vallee, Methods Erzzymol., 1967, 11, 565.L. Wofsy and S. J. Singer, Biochem., 1963,2, 104.S. M. McElvain and J. W. Nelson, J. Amer. Chern. SOC., 1942, 64, 1827.K, L. Carraway and D. E. Koshland, Methods Enzymol., 1967, 11, 616.ti H. Fraenkel-Conrat and H. S . Olcott, J. Biol. Chern., 1945, 161, 259C. H. ROCHESTER AND A. V. WESTERMAN 43* J. Bello and J. R. Vinograd, J. Amer. Chem. SOC., 1956, 78, 1369.C. H. Rochester and A. V. Westerman, J.C.S. Faraday I, 1976, 72,2753.P. G. Squire, P. Moser and C. T. O’Konski, Biochemistry, 1968, 7,4261.lo P. F. Spahr and J. T. Edsall, J. Bid. Chem., 1964,239,850.l2 R. Brodersen, B. J. Haugaard, C. Jacobsen and A. 0. Pedersen, Acta Chem. Scand., 1973, 573.l3 I. C. Watt and J. D. Leeder, Trans. Faraday Suc., 1964,60, 1335.l4 C. €3. Baddiel, M. M. Breuer and R. Stephens, J. Colloid Interface Sci., 1972, 40,429.l5 I. C. Watt and J. D. Leeder, J. TextiZe Inst., 1968, 59, 353.l6 M. J. Hunter and M. L. Ludwig, J. Amer. Chem. Suc., 1962, 84, 3491.l 7 R. W. Green and K. P. Ang, J. Amer. Chem. Sue., 1953, 75, 2733.l 8 E. F. Mellon, A. H. Korn and S. R. Hoover, J. Arner. Chem. Suc., 1947, 69, 827.l9 C. Tanford, S. A. Swanson and W. S. Shore, J. Amer. Chem. Suc., 1955, 77, 6414.2o C . Tanford, J. G. Buzzell, D. G. Rands and S. A. Swanson, J. Amer. Chem. Suc., 1955,77,6421.21 C. J. Clemett, personal communication.(PAPER 6 /908

ISSN:0300-9599    

DOI:10.1039/F19777300033

出版商:RSC    

年代:1977

数据来源: RSC

摘要:

Standard Free Energy of Transfer of Ionic Surfactantsfrom Water to Water + Acetone Mixtures from VapourPressure MeasurementsB Y CLAUDE TREINER" AND A. LE BESNERAISLaboratoire d'Electrochimie, UniversitC P. et M. Curie,4, Place Jussieu, 75230 Paris Cedex 05, FranceReceived 13th May, 1976The standard free energy of transfer, AGi of sodium decylsulphate (SDS) and of decyltrimethyl-ammonium bromide (DTMABr) from pure water to mixtures of water and acetone (AC) have beendetermined by accurate vapour pressure measurements of dilute solutions at 298.15 K. Preciseconductance measurements were also made for the two ionic surfactants in water and in water + ACmixtures in the same solute concentration range. AC? was negative, went through a minimum andincreased in the AC rich mixtures for both ionic surfactants.These results are qualitatively similarto those for tetrabutylammonium bromide which forms no micelIes in the same solvents ; they arealso consistent with the results inferred from critical micelle concentration (c.m.c.) data on dodecyltri-methylammonium bromide in the same binary solvent system. Using an extrathermodynamicapproach for assignment of AG; single ion values, it is shown that these experimental findings canbe accounted for solely by the opposing behaviour of anion and cation towards the solvent molecules.Comparison of AG for SDS and DTMABr (which are almost equal over the whole AC concentrationrange) indicates that the contribution of the OSO; group is of the same sign (positive from waterto water+AC mixtures) and virtually equal to that of the bromide ion.It is well known that the variation of critical micelle concentration (c.m.c.) as afunction of chain length of surfactants in water is similarto the dependence of the solubility of n-alkanes (for example) in the same solvents.So, to a first approximation, the c.m.c.may be regarded as a " solubility " and thedriving force for micelle formation may be directly related to the properties of eachions of the surfactant. However, in the presence of organic additives, direct com-parison between c.m.c. and solubility data may be misleading: the high solubilityof many ionic surfactants in aqueous solutions compared with the low value of thec.m.c. precludes any attempt to separate excess and standard free energies in theformer case.Most information is thus derived from c.m.c. experiments alone.Interpretations of the variation of c.m.c. on addition of organic solvents are thusmost often based on assumed changes in the micelle i t ~ e l f , ~ ' ~ whether through itsdestruction or its penetration by the organic molecules, sometimes taking into accountthe change in the dielectric constant of the In particular, the possibilityof opposing behaviour of the anions and cations (preferential solvation) of thesurfactant towards the aqueous binary system is not generally disc~ssed,~ as thestandard partial molar free energies of the surfactant components are not known.We have recently lo* 'I determined the standard free energy of transfer AG," oftetrabutylammonium bromide (n-Bu,NBr) from water to water +acetone (AC)mixtures using a vapour pressure method.It was shown that the change of AG," withsolvent composition could be essentially accounted for assuming that the contributionof the organic cation could be calculated using the scaled-particle theory and that44or in salt solution 2 C . TREINER AND A . LE BESNERAIS 45of the anion ascribed to an electrostatic effect. The purpose of the present investiga-tion was to apply these ideas to ionic surfactants, which are chemically relatedcompounds, in the same solvent mixtures ; it was also thought interesting to compareAG," values obtained from c.m.c. data and by a vapour pressure method used atpre-micellar concentrations.As a consequence, the c.m.c. of the ionic surfactantschosen had to be high enough to avoid pre-micellar aggregation at the solute con-centration compatible with precise vapour pressure measurements, but not too highfor meaningful comparison with c.m.c. experiments ; for these reasons we have chosensodium decylsulphate (SDS) and decyltrimethylammonium bromide (DTMABr).The co-solvent is acetone (AC). Previous studies of single ion free energies oftransfer of simple 1 : 1 electrolytes have been made in water + AC mixtures,12 andsome c.m.c. experiments for ionic surfactants are known in these solvents.5* 9 - l3# l4Finally these compounds are well suited to vapour pressure measurements.THEORYGrunwald and Bacarella l5 have shown that the rate of change of the standardchemical potential Go of an electrolyte completely dissociated into free ions can beobtained (on the mole fraction scale) from the relationship(1)1000 a In (u,/u,) dlnY* %[ am 1, = & ~ + 2 ~ ~ ) m - 2 ~ ~ r ( ~ ) z l *al and a2 are the activities of each solvent, y* is the solute mean activity coefficient(yk + 1 when m + 0), rn its molality, Z1 the water mole fraction (Zl+Z2 = I),and r = (MI -M2)/M12, M l z = MIZl + MzZz where M1 and M2 are the molecularweight of each solvent.It has been shown 16* l7 that by measuring a G o / Z l forseveral values of Z1 and integrating the curve obtained, one can calculate the standardfree energy of transfer of a solute from a reference solvent (here water) to the differentsolvent mixtures.The method used to obtain BGo/dZl has been described previously in detail.16It has been shown that provided the solute is sufficiently diluted for y k to be calculatedby the Debye-Huckel equation, then the vapour phase composition y in equilibriumwith the solution can be calculated from the variation of the total pressure P withsolute concentration m using the Gibbs-Duhem equation.The activities a, and a2are then readily obtained assuming that the vapour behaves as an ideal gas(py and pg are the pure solvent vapour pressures). The introduction of the secondvirial coefficient of the gas mixture in the calculations results in a change of aGo/Z,well within experimental error.17* l 8 BGojaZl is finally calculated using eqn (1)again with the activity coefficient of the electrolyte obtained using the Debye-Huckelequation; the integration of BGo/8Zl with respect to 2, is performed analytically.EXPERIMENTALThe mixed solvent was degassed by freezing with liquid nitrogen, pumping and melting(5 cycles were necessary) in a 1 dm3 Pyrex flask; 5 cups containing the surfactant sampleswere added under vacuum to the solvent mixture using a cup dispensing device.The flaskwas thermostated at 25.000+0.003"C. The total pressure was measured on a TexasInstruments gauge with a sensitivity of 0.005 Torr46 AG," OF IONIC SURFACTANTSREAGENTSDTMABr (Eastman Kodak) was recrystallized three times from pure acetone and driedunder vacuum. SDS (Merck 99 %) was used without purification. Acetone (Merck,water content < 0.03 %) was used without purification; conductance water was used forthe acetone+ water mixtures.RESULTSIt was essential for our vapour pressure method that the highest surfactantconcentration be below the c.m.c.values. These are 0.0646 and 0.035 mol kg-1 forDTMABr and SDS respe~tive1y.l~ Both are known to increase initially with theaddition of acetone, so we never exceeded m = 0.02 mol kg-l in our experiments.Pre-micellar association of surfactants in water has been assumed by a numberof author^.^ The effect of such a phenomenon in our case could be accounted forby a correction term in the Debye-Hiickel activity coefficient law which is used ineqn (1). However, even if some association of like charges occurs (dimers or trimers)the degree of association has been found to be small for surfactants of the type wehave studied ;20* 21 moreover, as their c.m.c. increase with addition of acetone, thedegree of association (which is related to the hydrophobic interaction) should beeven smaller in the mixed solvent used.In order to test further the importance ofthe dimerization phenomenon in the solute concentration range studied, we havemade a number of precise conductance measurements both in water and in an80 wt % water+acetone mixture. The data were treated by the complete Fuoss-Onsager equation as previously described.22 Table 1 presents a sample of theresults obtained. Inspection of the standard deviations reveals no systematic trendor anomalies : the solutes seem to behave as ordinary 1 : 1 electrolytes.We havethus assumed that no correction due to any aggregation of like charges has to bemade in the calculation of aG,/Z,.It has been shown previously lo that in the solute concentration range studied,the total pressure and vapour phase composition change with molality can beiepresented within experimental error by the linear relationshipsP =p,+kmy = yo+k'm (3)where po and yo are, respectively, the total pressure and mole fraction vapour phaseof AC with no solute. Tables 2 and 3 present the results obtained together with thestandard deviations (least-square curve fitting).The d G o / Z l values are the average of 3 or 4 experimental determinations. Thedata were treated assuming no short range ion-ion interactions (KA = 0) since whenthe ions are associated into ion pairs, eqn (1) may be written aswhere y$ is the mean activity coefficient of the free ions and a the degree of association.The derivative of a with respect to Z1 cannot be obtained experimentally with a highdegree of accuracy, especially when the association constants are rather small, soany attempt to take this effect into account results in a lower precision in aG,/aZ,in the present case.The error introduced by ignoring the association phenomenacan be evaluated by comparison with the careful study of de Ligny et al. on thesolubility of 1 : 1 electrolytes in hydro-organic mixtures,23 who take into account thedegree of dissociation of the ions in their calculation. The accuracy of AG," for thC .TREINER AND A . LE BESNERAIS 47TABLE 1 .-CONDUCTANCE OF SURFACTANTS IN AQUEOUS SOLUTIONS AT 298.15 KSDS n-DTMABrwater a 104c/mol-l dm-3 AlQ-1 cmz dm-3 lO4c/mol--1 dm-3 A/f2-1 cm* dm-3302.622 63.781229.5 56 65.022139.347 66.83786.035 68.30534.216 70.404A, = 74.55f0.03 SZ-'KA = 0GA = 0.015145.606 91.153117.414 92.32493.027 93.29753.165 95.70035.014 97.01421.781 98.196A, = 102.46+_0.02 i 2 - IKA = 2.7f0.3~TA = 0.02580 % AC lO4c/mol-1 dm-3 A/Q-1 cmz dm-3 lO4c/mol-1 dm-3 AjQ-1 cm2 dm-3109.665 50.62964.874 54.48441.866 57.54429.556 59.73019.666 62.1231 1.753 64.469A. = 73.3k0.3 C2-lKA = 51f2OA = 0.06611 1.872 59.72595.709 61.20343.582 67.42127.894 70.44515.01 7 73.812A, = 83.950.1 i2-'KA = 40fr2OA = 0.043a D = 78.54, q = 0.008 903 P ; b D = 29.6, q = 0.006 26 P ; C OA is the standard deviation of a run.TABLE 2.-cHARACTERISTIC PARAMETERS FOR VAPOUR-LIQUID EQUILIBRIUM a DECYLTRIMETEIYL-AMMONIUM BROMIDE IN WATER+ ACETONE MIXTURES AT 298.15 K--AGO/Z1 PolTorr Yo - k C -k'X102C k3 mol-1 J mol-11 .o0.98480.97460.96660.92790.82830.68330.44550.3658-51.6261.9972.03110.15159.02183.083 99.85205.80-0.52170.61330.67540.80600.86890.89010.90750.9082-4.5k0.314.8 f 0.118.7k0.941.5kO.126.6fr 0.19.7 f 0.9-9.3k1.1- 9.3 f 0.8I2.6k0.48.2f0.17.7k 0.47.3 k0.51.9kO. 1 o.o+ 0.0- 3.2f0.2- 3.4k0.1-12.2 k 0.544.3 f 0.648.8+ 1.751.8k 1.317.5 k 0.6- 3.1 fr 0.4- 23.3 & 0.6-26.8k 1.00953 5078521006555749040652685The values of dielectric constant D of the water + acetone mixtures necessary for the calculationof the activity coefficient were taken from ref.(23) ; b see ref. (10) ; C coefficients for eqn (3).TABLE 3 .-CHARACTERISTIC PARAMETERS FOR VAPOUR-LIQUID EQUILIBRIUM : a SODIUM DECYL-SULPHATE IN WATER + ACETONE MIXTURES AT 298.1 5 K- k C --0 - - - - - 1 .o0.9834 50.41 0.5217 6.0+ 0.1 4.1 0.1 20.4k0.2 1700.9294 108.66 0.8054 35.5+ 3.0 6.1 f 0.5 50.2fr1.3 24000.8301 161.33 0.8688 37-25 1.6 3.050.2 26.25 1.0 62500.6854 186.36 0.8901 10.1 k0.4 O.O+ 0.0 - 2.6f 0.2 75700.4489 200.88 0.9075 - 12.5k0.7 - 3.0f0.1 -24.9k0.4 43100.3650 204.58 0.9082 - 17.650.9 -4.7fr0.2 -35.2+ 1.0 1690a b C See footnotes to table 248 AGP OF IONIC SURFACTANTS2 surfactants is then estimated to be of the order of f 50 J mol-l in the water-richregion and increases up to about +400 J mol-I in an 85 wt % water+AC mixture.DISCUSSIONThe main characteristics of our experimental results may be summarized asfollows : (a) AG," from water to water +AC mixtures is negative, passes through aminimum and increases in the AC-rich mixtures for the 2 ionic surfactants.Inaddition, an inflection point appears in the water-rich region, which corresponds tothe maximum in the variation of 8Go/8Zl with Z1 (see tables 2 and 3). The samebehaviour was found for tetrabutylammonium bromide which does not form micellesin these solvents (see fig. 1) lo and also in water+tetrahydrofuran and water+acetonitrile mixtures.ll So, from the view point of standard free energies, there isno qualitative difference between the 2 surfactants and the tetra-alkylammonium salt.(b) AG," is almost equal numerically for the 2 surfactants in the whole AC concentrationrange studied.These 2 points will now be considered in relation to the variation ofthe c.m.c. of surfactants with organic additives.I1.0 0.8 0.6 0.4FIG. l.-AGi (on mole fraction scale) as a function of mole fraction of water for n-Bu4NBr andn-DTMABr in water + acetone mixtures, from vapour pressure measurements. Upper curve,n-Bu4NBr ; lower curve, n-DTMABr.RELATION BETWEEN AG; AND c.m.c. CASE OF DTMABrThe results presented in tables 2 and 3 make use of the reasonable assumptionthat there is no pre-micellar aggregate at the surfactant concentration used in ourexperiments.The standard free energy of transfer of ionic surfactants may, inprinciple, be deduced from the variation of their c.m.c. on addition of organicmolecules. If it is assumed that the chemical potential of the surfactant in themicelle phase is equal to the chemical potential of the surfactant in the bulk phaseC . TREINER AND A . LE BESNERAIS 49and that the standard chemical potential of the surfactant in the micelle is independentof solvent composition, then eqn (5) may be applied ' 9 24c.m.c., fwc.m.c., fs AGP = 2RT In - +2RT In -where c.m.c.,, fw, c.m.c., and fs refer respectively to the c.m.c. and the activitycoefficient of the surfactant in water and in the mixed solvents.f w and fs can becalculated using the Debye-Huckel equation.We wanted to compare AG," obtained fr0m.c.m.c. and vapour pressure measure-ments. Unfortunately there are no c.m.c. data for the surfactants we have studied inwater + AC mixtures, so we have used instead for comparison with our results, those ofMiyagishi on dodecyltrimethylammonium chloride (DOTMACl) who apparentlycould observe a c.m.c. in the same solvents at 35°C up to a mole fraction of AC ofZ, =0.3. The c.m.c. of this surfactant in water was too low to permit precise vapour pres-sure measurements, but, as the change of the ratio c.m.c.,/c.m.c., with temperature, -.E-4 tI \\\\0.0 0 1 0.2 0.3Iz2FIG.2.-Comparison of A G values (on molarity scale) in water + acetone mixtures for n-DTMACI(as obtained from our vapour pressure method at 25°C) and n-DOTMACl [as obtained from c.m.c.data at 35°C using eqn (5)]. -, n-DTMACl ; - - - , n-DOTMACI.is rather ~ r n a l l , ~ we believe that the comparison between AG," as obtained from the2 methods will be significant, the only difference between the 2 surfactants being twoCH, groups. Using the experimental results of Miyagishi, AG," was calculated usingeqn (5). To make a more direct comparison between the c.m.c. and vapour pressuredata we have transformed our results on DTMABr into DTMACl using the additivityrule and the standard e.m.f. results of Bax et at.25 on HCI and HBr in water+ACmixtures. Fig. 2 presents thevariation of AG," with AC mole fraction for the 2 ionic surfactants, obtained fromvapour pressure and c.m.c.experiments. There is a clear parallelism between the2 curves. As expected AG," is more negative for DOTMACl, with two more CH2Finally, these were recalculated on the molar scale50 AG," OF IONIC SURFACTANTSgroups, than for DTMACl. A minimum is observed for both surfactants. Theminimum of the AG," function corresponds to the maximum of the AGO functioncorresponds to the maximum observed for the variation of c.m.c. with solventcomposition in the case of DOTMAC1.14 Because of the temperature differencebetween the 2 sets of data, comparison of the respective positions of the minima forAG: is not significant ; also, the value of 2, for which the minimum occurs dependson the concentration scale chosen for the calculation of AG,".When changing frommole fraction (table 2) to molarity scale (fig. 2) this value is shifted to lower 2,values [see ref. (26) for a discussion on the " cratic " factor].The similarity between the curves presented in fig. 2 for the 2 ionic surfactants isinteresting as it suggests that we do not need to consider the influence of the organicadditive on the micelles in order to explain the essential characteristics of the variationof c.m.c. with AC concentration. In particular, the fact that AG," goes through aminimum can easily be interpreted in a manner analogous to that proposed previouslyfor n-Bu4NBr.l0. l1 Bax et a l l 2 using an extrathermodynamic approach haveshown that the standard free energy of transfer of Br- (or Cl-) is positive from waterto water + AC mixtures (preferential solvation by water molecules).This behaviouris very common for the transfer of inorganic anions from water to aqueous binarymixtures. 27-3 *It follows that AG,"(+) for the individual organic cation is negative from waterto water +AC mixtures ; this behaviour is characteristic of aliphatic groups in thesemedia and has been attributed, in part, to the difference in the work of cavity formationin water and in the mixed solvents, as can be calculated, for example, by the scaled-particle theory.ll As the variation of AGF with solvent composition for each ion isgenerally not linear, the minimum observed in fig. 2 can be looked upon simply as aconsequence of the opposing behaviours of the anion and cation.The same obser-vation has been made for n-Bu4NBr in the same water+AC solutions.AG," is more negative for n-DTMABr than for n-Bu4NBr in the AC concentrationrange studied (fig. l), although there are three more CH2 groups in the former case thanin the latter. This may be interpreted as evidence for a larger cavity effect for a linearaliphatic chain than for a spherical solute with (nearly) the same number of CH2groups. Alternatively, one could argue that the van der Waals forces between theorganic ion and the AC molecules should be larger in the case of an aliphatic chainwhere all the CH2 groups are exposed to the solvent than in the case of a morespherical solute where some of the CH, groups are shielded.This ambiguity isinevitable in any theory which considers the effect of a solute in a solvent as made upof a cavity (volume) term and a specific interaction term : it is one of the weaknessesof the theory, especially when applied to non-spherical molecules (solute or solventmolecules). After the minimum value of AG," has been reached, a new trend isobserved. AG," increases for both electrolytes as the effect of the bromide ion becomespredominant, but the increase is faster for the surfactant than for n-Bu,NBr. Thisnew trend must be the consequence of ahead-group effect of the surfactant.The coulombic effect predicts a positive contribution to AGF from water towater + AC mixtures according to the equationwhere D, and Do are, respectively, the dielectric constant of the solvent mixture andpure water and the other symbols have their usual meaning.This contribution isopposite to that of the cavity effect : it is larger for the tri-methylammonium group,which has a smaller r+ radius than the tetrabutylammonium ion, and must be addeC . TREINER A N D A . LE BESNERAIS 51to the same electrostatic contribution due to the bromide ion. Thus AG,"(+, for thesurfactant tends to level off while that of the tetrabutylammonium ion decreases.Ralston and Hoerr 31 have measured the solubility of hexyl- and decylammoniumchloride in aqueous ethanol. They found a maximum solubility (minimum AG,) forthe dodecyl salt, which forms micelles in these solutions, but no maximum for thehexyl salt which forms no micelles.They concluded that the maximum observed[which is also found for sodium dodecylsulphate (SDOS) in water + dioxan mixturesfor example] is related to micelle formation. This interpretation is not necesserilycorrect. In order to get a minimum for AG," at a particular 2, value, contributionsfrom the anion and cation of the same order of magnitude are required. If theabsolute value of AG," for one ion of the electrolyte is very different from the other,than the minimum disappears. For example AG," for tetramethylammonium bromide(Me,NBr) is positive from water to water+AC mixtures l 2 withwhereas a minimum is found for n-Bu4NBr for whichIAG, (n-Me,N+)I < lAG,"(Br-)lIAGt(n-Bu,N+)I = lAG:(Br-)l.Qualitatively the same situation may occur for the hexyl- and dodecylammoniumchlorides. We know from extrathermodynamic assumptions that the free energy oftransfer is positive for the chloride ion from water to water +ethanol mixtures.28* 30The effect of this ion must be predominant in the whole ethanol concentration range(the solubility decreases from pure water to pure ethanol) for the salt with the smallestaliphatic hydrocarbon tail; it should be of the same order of magnitude for theanion and cation in the case of the dodecylammonium salt, the contribution of CH,groups to AGP for the transfer from water to ethanol being negative.32COMPARISON BETWEEN DTMABr AND SDS I N WATER+AC MIXTURESThe AG," values are very similar for DTMABr and SDS over the whole ACconcentration range.Emerson and Holtzer made the same observation for thec.m.c. of DOTMABr and SDOS in dilute AC solutions (Z2 < 0.08). We proposethe following explanation: each ionic surfactant might be considered, to a firstapproximation, as a 3 component electrolyte having a hydrocarbon tail, a positiveion and a negative ion. Then for our 2 surfactantsAG,"(DTMABr) = AG,"(Me,N+) + AG,"[(CH,>,] + AG,"(Br-)AG,"(SDS) = AG,"[CH,(CH,),] + AGtO(OS0;) + AG:(Na+).We have no single ion values for the Na+ ion but we have the data of Bax et a2.l2for the K+ ion; the behaviour of these 2 ions is very similar in aqueous systems.It can be seen then l 2 that the single ion values for Me,N+ and K+ are both positiveand almost equal from water to pure AC.Further, we can safely assume that thecontributions of the hydrocarbon tails of both surfactants having (nearly) the samenumber of carbon atoms are of the same order of magnitude. It follows that thecontribution to AG," of the OSO, group of SDS and the Br- contribution of DTMABrmust be of the same sign and numerically similar. This seems reasonable whencompared with the similar behaviour of inorganic anions such as the perchlorate ionin the same solvents. Fig. 3 compares the single ion free energies of transfer ofsome of the electrolytes discussed in this study.In conclusion the minimum in AG,O observed for SDS in water+AC mixtures isa consequence of the opposing behaviour towards the solvent of the 3 different part52 AG," OF IONIC SURFACTANTSof the surfactant. The hydrocarbon tail and the positive ion (Na+) contributionsare both negative because of a cavity effect for the aliphatic groups, as can be shownby Pierrotti's scaled particle theory,33 and a preferential solvation effect for Na+ bythe AC molecules ; these 2 effects dominate in the water-rich region [AG,"(CH3(CH2)J< 0, AGf(Na+) < 01.The contribution of the OSOY group to AG," [AG,"(OSO,) > 0must dominate in the AC-rich mixtures. The sum of these 2 opposing contributionsis again responsible for the minimum in the AGF function. In the case of solubilityor c.m.c. experiments a maximum would then be observed, as indeed is the case forthe solubility of SDOS in water + dioxane or dodecylammonium chloride in water +ethanol mixtures.0 0 2 0 4 0 62 2FIG.3.-Single ion AG; values in water + acetone mixtures (mole fraction scale) using the extra-thennodyanmic approach of Bax e f a1.12 (a) Br-; (b) n-Me4N+; (c) n-Bu4N+; ( d ) n-DTMA+.The main conclusion of this study is that the variation of the c.m.c. of ionicsurfactants with organic additives could be evaluated from a knowledge of thestandard free energies of the constituents of the surfactant. The interpretationwe have proposed for the variation of c.m.c. on addition of a typical organic additivesuch as acetone should apply to all organic additives which initially increase thec.m.c. of ionic surfactants. The case where the additive decreases the c.m.c. throughan assumed penetration of the micelle, as in the case of alcohol additives, will bediscussed in a forthcoming paper.C.Tanford, The Hydrophobic Bond (Wiley, New York, 1973), p. 14.P. Mukerjee, J. Phys. Chem., 1965, 69,4038.G . C. Krescheck, in Wafer, ed. F. Franks (Plenum Press, 1974), vol. 4, p. 99.Ref. (l), p. 46.M. F. Emerson and A. Holtzer, J. Phys. Chenz., 1967, 71, 3320.K. Shiramaya and R. Matuura, Bull. Chem. SOC. Japan, 1965, 38, 373.K. Shiramaya, M. Hagashi and R. Matuura, Bull. Chem. SOC. Japan, 1969, 42,1206.S . Miyagishi, Bull. Chem. SOC. Japan, 1976, 49, 34.lo C. Treiner and P. Tzias, A&. Chem. Ser., in press.C. Treiner, P. Tzias, M. Chemla and G. M. Poltoratskii, J.C.S. Faraday I, 1976,72,2007.l 2 D. Bax, C. L. de Ligny and A. G. Remijnse, Rec. Trau. chem., 1972,91, 1225.l3 S. Miyagishi, Bull. Chem. SOC. Japan, 1974, 47, 2972.ti N. Nishikido, Y . Moroi, H. Vehara and R. Matuura, Bull. Chem. SUC. Japan, 1974, 47, 2634C. TREINER AND A . LE BESNERAIS 53l4 S. Miyagishi, Bull. Chem. SOC. Japan, 1975, 48, 2349.j 5 E. Grunwald and A. L. Bacarella, J. Amer. Chem. Soc., 1958, 80, 3840.l 6 C. Treiner, J. Chim. phys., 1973, 70, 1183.l7 C. Treiner and P. Tzias, J. Solution Chem., 1975, 4, 471.l8 G. Baughman, E. Grunwald and G. Kohnstam, J. Amer. Chem. SOC., 1960, 82, 5801.2o 8. J. Birch and D. G. Hall, J.C.S. Faraday I, 1972, 68,2350.2 1 J. S. Clunie, J. F. Goodman and P. C. Symons, Trans. Faraday Suc., 1967, 63, 754.22 J. C. Justice, R. Bury and C. Treiner, J. Chim. phys., 1968, 65, 1708.23 C. L. de Lighy, D. Bax, M. Alfenaar and M. G. L. Elferink, Rec. Trav. chim., 1969, 88, 1183.24 W. B. Gratzer and G. H. Beaven, J. Phys. Chem., 1969, 73,2270.2 5 D. Bax, C. L. de Ligny, M. Alfenaar and N. J. Mohr, Rec. Trm. chim., 1972, 91, 601.26 R. W. Gurney Jr., Ionic processes in solution (McGraw-Hill, New York, 1953).27 C. F. Wells, J.C.S. Faraday I, 1974, 70, 694.D. Bax, C. L. de Ligny and A. G. Remijnese, Rec. Trau. chim., 1972, 91, 965.29 C. Treiner and P. Finas, J. Chim. phys., 1974, 71, 67.30 0. Popovych, Analyt. Chem., 1974,46,2009.31 A. W. Ralston and C. W. Hoerr, J. Amer. Chem. SOC., 1946, 68, 851.32 E. J. Cohn and J. T. Edsall, Proteins, Amino acids and Proteins (Reinhold, New York, 1943).33 R. A. Pierrotti, J. Phys. Chem., 1963, 67, 1840.P. Mukerjee, Complete table of critical miceile concentrations (N.B.S., Washington, 1967).(PAPER 6/917

ISSN:0300-9599    

DOI:10.1039/F19777300044

出版商:RSC    

年代:1977

数据来源: RSC

摘要:

Homogeneous Isotope Exchange ReactionsPart 3.-H2S+D,BY GRAHAM PUTT* AND DAVID ROGERSSchool of Molecular Sciences, University of Sussex, Brighton BN1 9QJReceived 24th May, 1976The kinetics of the early stages of the exchange reaction in H2S + D2 mixtures [H2S, 0.55-9.34 Torr(1 Torr = 133 N m-2) ; D2, 0.55-6.39 Torr] have been studied in a static system at 808-937 K. Theeffects of excess argon and surface to volume (slu) ratio were studied. The initial rate is independentof s/v and in the absence of Ar is described bywhered[HDS]/dt = +k[H2S][D2]*loglo(Sk/dm3 mol-.& s-l) = 12.10+ 0.25-(11 860+ 220)t/(T/K).The results are in agreement with a homogeneous radical chain mechanism, initiated and terminatedheterogeneously. The rate constants for3HSHZS -> HS*+HZ6HS.+ D2 -+ HDS + Ddeduced arelog10(k3/dm3 mol-' s-l) = 10.44+0.25-(330& 220)/(T/K)logl,(kb/dm3 mol-' s-l) = 10.13 +-0.25-(3530_+220)/(T/K).To our knowledge there has been no previous study of H2S/Dz exchange in astatic system at high temperatures. A single pulse shock tube (S.P.S.T.) study ofthe first 20 % reaction in excess Ax at 1260-1590 K was interpreted in terms of a fourcentre molecular mechanism involving vibrationally excited reagents. Several studieshave been made of the reaction of H with H2S at low temperatures by flow dis-charge 2 s and f i s h photoly~is.~-~ No high temperature kinetic data is availablefor this reaction.EXPERIMENTALAPPARATUSThe conventional static system and reaction vessels a and b have been described?.OREAGENTSResearch grade D2 (Air Products >99.99 %) was purified by diffusion through nickel.'High purity Ar (Air Products 99.998 %) was purified by several freeze-pump-thaw cycles andby passage over spluttered sodium. O2 was < 10 p.p.m. H2S was prepared from sodiumsulphide and conc. sulphuric acid, dried over P205, and purified by five freeze-pump-thawcycles and fractional distillation. Mass spectrometric analysis showed no traces of 02,H20 or higher sulphides (< 10 p.p.m.).t = Ea/2.303 R. All errors are standard deviations.5G . PRATT AND D. ROGERS 55ANALYSISMass spectrometric analysis of H2S+ HDS+ D2S mixtures is complicated by the foursulphur isotopes. At ionisation energies < 14.4 eV, fragmentation was negligible and therelative isotopic abundances were thus found.The 70eV cracking patterns of HDS andD,S were calculated assuming that molecular ions have the same intensities and the prob-ability of D loss is 0.44 times that of H 1 0 ~ s . ~ Calibration accuracy was verified by analysisof reacted mixtures containing large percentages of HDS and D2S at both 70 eV and 11 eV.The analyses for H2S, HDS and D2S agreed within 4%. For all subsequent quantitativeanalyses m/e = 34 to 36 were used at 70 eV.RESULTSQualitative analysis showed that Sz products were not formed (<0.01 %>. Thedeuterated hydrogen sulphides were formed consecutively (fig. 1) and the initial ratefor HDS was equal to that for HD (fig. 1). This is good evidence that there is no100 600 1200timeisFIG.1.-Formation of reaction products for conditions T = 855 K, [H2S]i = 0.56 Torr, [DJi =0.56Torr. 0 HDS, HD, point common to both, 0 D2S. Inset: Formation of D2S forconditions T = 937 K, [H,S]i = 0.57 Torr, [Dz]i = 0.57 Torr, showing the acceleration of rate ofproduction in the initial stages.c 30 1.0 2.0In(P/Torr)FIG. 2.-Ln/ln order plot of initial rate against total pressure at T = 937 K, [H2S], = [Dzlj, vessel b.The solid line has a slope of 1.556I I0 1-0 2 0 3.0ln([H2S]t = o/Torr)FIG. 3.-Ln/ln order plot of initial rate against hydrogen sulphide pressure at T = 896 K, [DzJi =0.60 Torr, vessel 6 . 0 without added inert gas, argon added to a total pressure of 31 Torr. Thesolid line has unit slope.-6.50.5 1.0 1.5In(CDzlt = o /Torr)FIG.4.-Ln/ln order plot of initial rate against deuterium pressure at T = 913.5 K, [HZSJi =0.60 Torr, vessel b. The solid line has a slope of 0.5G. PRATT AND D . ROGERS 57exchange of HDS in the mass spectrometer or inlet system during analy~is.~ Noinduction period is detectable in HDS or HD production in fig. 1. In all subsequentkinetic studies the extent of reaction was limited (< 10 %) so that [D2S] was negligible.ORDERS OF REACTIONExperiments with stoichiometric mixtures gave good +-order plots (fig. 2). Thepartial orders w.r.t. H2S and D2 are 1.0 and 0.5 respectively (fig. 3 and 4). In con-trast to CH4/D2 exchange lo there is no curvature in these plots at high [H2S]/[D2]ratios. The initial rate is described byd[HDS]/dt = +k[H2S][D2]+ (1)over the whole range of reactant pressures studied.105 1-10 1.15 1.20103 KITFIG.5.-Arrhenius of plot sk. 0 s/v = 1.4 cm,-' s/v = 6.0 crn-l.INERT GAS ADDITIONFig. 3 shows the effect of addition of excess argon to a constant total pressure.The rate is unaffected at low [H,S]/[D2] ratios, but is reduced at high [H2S]/[D21ratios.S/V CHANGEChanging s]v from 6.0 to 1.4 cm-l had no effect on & (fig. 5).EFFECT OF TEMPERATURE+k was measured at 12 temperatures in the range 808-937 K (table 1). The leastlog,,(&/dm3 mol-1 s-l) = 12.10+0.25-(1 I 860+220)/(T/K).mean squares Arrhenius fit is58 H2S + DzTABLE 1 .-MEASURED $-ORDER RATE CONSTANTS FOR STOICHIOMETRIC MIXTURES AND DERIVEDVALUES OF k3 AND k6templK i808.0821.5821.5821.5836.5836.5836.5841.5841.5848.5848.5848.5860.0860.0860.0870.5870.5870.5874.0874.0883.5883.5883.5896.0913.5913.5913.5913.5937.0937.0937.0937.0937.0ressel*bbbbbbbabbbbb0bbbahbbbabbbbbbbaaa3kldmQ mol-f s-12.530(- 3)t5.197(- 3)4.779( - 3)4,859(- 3)7.816(- 3)8.618(- 3)9.765(- 3)9.824( - 3)1.001 (- 2)1.414(- 2)1.1 1 8( - 2)1.333(- 2)1.705(- 2)1.827(- 2)2.052( - 2)3.012(- 2)3.101(-2)2.701(- 2)2,976(- 2)3.583(- 2)4.53 8 (- 2)4.236(- 2)4.690(-2)7.71 5( - 2)1.333(- 1)1.361(- 1)1.731(- 1)1.750(- 1)2.131(- 1)2.559( - 1)2.448(- 1)2.261(- 1)2.476(- 1)k6/dm3 mol-1 s-*5.645(5)7.848(5)7.217(5)7.3 3 8(5)7.763(5)8.559(5)9.699(5)8.5 1 3(5)8.675(5)1-01 5(6)8.026(5)9.570(5)9.693 (5)1.089(6)1.221 (6)1.257(6)1.095(6)l.lM(6)1.330(6)1.330(6)1.242(6)1.374(6)1.669(6)1.910(6)1.952(6)2.485(6)2.512(6)1.806(6)2.169(6)2.075(6)1.916(6)2.098 (6)9.045(5)k3/dm3 mol-1 s-11.032(10)1.236(10)1.137(10)1.1 55( 1 0)1.042(10)1.148 (1 0)1.302(10)1.084(10)1.105(10)1.203(10)9.51 1(9)1.134( 10)9.545(9)1.022( 10)1.148(10)1.11 6(10)1.196( 10)1.042 (1 0)1.016(10)1.224(10)1.1 17( 10)1.044(10)1.155(10)1.249(10)1.221(10)1.248(10)1.589( 10)1.607( 10)9.439(9)1.134(10)1.084(10)1.002( 10)1.097(10)* a, slv 1.4 cm-' ; b, slv 6.0 cm-'.f- x(y) = x x 1Oy.DISCUSSIONProduct analysis establishes the stoichiometry of the reaction studied kineticallyasH2S +D2 = HDS +HD.It is not possible to say whether the four centre mechanism contributes to our mea-sured rate to a small extent. The rate predicted for the four centre process by therate expressions obtained in S.P.S.T. work for our typical conditions (H2S = 1.0Torr, D2 = 0.6 Torr, Ar = 26.4 Torr, T = 896 K) is two orders of magnitude lessthan the observed rate of exchange. Some other mechanism must account for thebulk of the observed reaction.The kinetic results have great similarity to those observed for CH4/D2 exchange loand strongly suggest a similar chain mechanism. In the methane exchange, initiationbyD2 -+ 2D (1G .PRATT AND D. ROGERS 59was shown to be negligible compared with dissociation of methane, even though bothprocesses are subject to surface catalysis. Initiation of the H2S exchange byis 57 kJ mol-l less endothermic than methane dissociation and should therefore bethe dominant radical generating step. The rapid processes,H2S + HS*+H (2)H+H,S --+ HS*+H, (3)H+D, + HD+D (4)will convert H to the main propagating species D and HS-.the propagating stepsFor long reaction chainsD+H2S + HD+HS- ( 5 )HS*+D2 -+ HDS+D (6)control the ratio [D]/[HS*] = k6[D2]/k5[H2S]. k6/k5 is close to K , [the equilibriumconstant for the reverse of step (3)] since the isotope effects will not be large. At900 K k6 Jk5 N K; = 3 x [using the thermodynamic data of ref.(I 1) and (12)].Hence [HS-] % ID] and of the terminations,2D -+ D2 (-1)D+HS*-+HDS ( 7 4or --+ HD+S (76)(34or -+ H,S+S (86)HS* + HS- 4 H,S,reaction (8) should be dominant if all processes are homogeneous. Previous work atlow temperatures 2-6 has favoured route (86) for the HS. combination step and route(7b) is included by analogy with this. However the reactionis known l 3 to have an activation energy of 21-29 kJ mol-I, and this analogy suggeststhat reaction (7b) is probably negligible compared with (7a). No S2 compoundswere detected in the products in this work. This observation is consistent with thelong chain hypothesis and provides no evidence for the relative rates of steps (80) andH+OH*-+ H,+O(3b)-The long chain steady state approximation yieldswhere R = [H2S]/[D2].Since k , < k,, comparison with the experimental rate law(I) shows that k-,/k, Q k5/k6 2: 3 x lo3 at 900 K, which is very reasonable, andk8/k7 << k6/k5 which is more difficult to understand. However, the effect of addingexcess Ar indicates that increasing ks [step (8) will be third order] causes the secondterm in the denominator of eqn (11) to become significant at large values of R, result-ing in the observed rate reduction (fig. 3). This in turn suggests that step (7) mustbe surface catalysed, otherwise no pressure dependence would be observed in (k,ks/k6k7). This conclusion is further supported by the observation that induction periodswere negligible. At the temperature (855 K) to which fig.1 refers this shows that boththe initiation and termination steps are at least 4 x lo4 times faster than the homo-geneous values predicted by the estimate of Burcat et al. for step (2) together with thecalculated equilibrium constant for the reverse step. The absence of s/u effect o60 HZS + D2,k is consistent with both steps (2) and (7) being surface catalysed, and this largecatalytic factor is sufficient to account for the above low ratio of k,/k,.The $-order rate constant may be written in terms of equilibrium constants ( K )and kinetic isotope effects f i = k 2 / k 7 , f2 = k-5/ks and f3 = k-3/166 as& = k,W2K,f,f,), (111),k = k3(K2KSflf2)+/K3f3. (IV)or,Thermodynamic data was taken from ref. (1 1) and (1 2), fl was calculated as before.OThe value is insensitive to the properties of the activated complex.lo f 2 andf3 werecalculated using an activated complex obtained by the 3 atom model BEBO method.14The properties of the complex are given in table 2 and the temperature variation off2 andf, is given in table 3. In Arrhenius form these calculated equilibrium constantsand kinetic isotope effects areK,/mol d n r 3 = 5.71 8 x lo3 exp[ - 45 509/(T/K)]K3 = 1.640 exp[ + 68 668/(T/K)]Ks = 2.662 exp[ + 73OO/(T/K)]fl = I. 1121 exp[ -290.2/(T/K)]2f2 = 1.0226 exp[ + 109.4/(T/K)]f3 = 1.2482 exp[ + 483.1 /(T/K)].1 2TABLE 2.-T)ROPERTIES OF ACTIVATED COMPLEX (H-H-sH)$ CALCULATED BY B.E.B.0.(3 ATOM MODEL) ; DATA FROM REF. (14) AND (15), UNITS CONSISTENT WITH EQUATIONS OFproperty an1V*/kJ rno1-IRl/AFl /dyn cm-1F22/dyn cm-lF12/dyn cm-lF4/ergD,/kJ mol-lPYP31A-lH-H-Sv*/cm-lVstr/cm-lvblcrn-1H-D-Sv* Icm-IVStJcm-lvbfcm-lv*/cm-lVstr/cm-lvb/cm-'D-D-SREF.(14)complex0.1275.531.2911.379- 0.1286(5)3.7747(5)0.0422(- 11)0.51 52(5)684.9i2208.7453.1497.0i21 82.9423.7488.0i1593.6321.3H2 HzS1 .oo0.745.73( 5)1.3464.28(5)457.71.0411.94(8)427737223054396.60.9321.723(8)Q These standard symbols are defined in ref. (14G . PRATT AND D. ROGERS 61TABLE 3 .-CALCULATED KINETIC ISOTOPE EFFECTST/K 650 700 750 800 850 900 9502f2 1.303 1.192 1.182 1.172 1.163 1.155 1.147f 3 2.610 2.483 2.375 2.283 2.204 2.135 2.074Hence from eqn (111)loglo(k6/dm3 mol-1 s-') = 10.13 5 0.25 - (35305 220)/(T/K).Using eqn (IV) givesloglo(k,/dm3 mol-l s-l) = 10.44+0.25-(330522O)/(T/K).No low temperature measurements of k6 are available for comparison.However,Arrhenius expressions for k , obtained previously arefor T = 243-368 K [ref. (3)] andlog1,(k,/dm3 mol-I s-l) = 9.89kO.05-(373+ 13)/(T/K)for T = 190-464 K [ref. (4)]. The agreement for the very low activation energy ofthis abstraction is certainly well within our relatively large experimental error, butour pre-exponential factor is higher though by less than two standard deviations.The rate constant for 808-937 K found here is some three times greater than predictedby the low temperature Arrhenius lines. This factor lies outside experimental errorand is consistent with the expected upwards curvature of the Arrhenius plot for anH atom transfer.A temperature dependence of the pre-exponential factor A =BT1s0 is sufficient to account for the curvature.10g10(k3/dm3 11101-l S-') = 10.01 f0.02-(367& 1 l)/(T/'K)We thank the S.R.C. for a maintenance grant (to D. R.).A. Burcat, A. Lifshitz, D. Lewis and S. H. Bauer, J. Chem. Phys., 1968, 49, 1449.J. N. Bradley, S. P. Trueman, D. A. Whytock and T. A. Zaleski, J.C.S. Faraday I, 1973,69,416.D. von Mihelcic and R. N. Schindler, Ber. Bunsenges Phys. Chem., 1970, 74, 1280.M. J. Kurylo, N. C. Peterson and W. Braun, J. Chem. Phys., 1971, 54,943.R. B. Langford and G. A. Oldershaw, J.C.S. Faraday I, 1972, 68, 1550.D. von Perner and Th. Franken, Ber. Bunsenges Phys. Chem., 1969,73,897.V. H. Dibeler and H. M. Rosenstock, J. Chem. Phys., 1963, 39, 3106.' G. L. Pratt and D. Rogers, J.C.S. Faraday I, 1976, 72, 1589.K. Biemann, Mass Spectrometry Organic Chemical Applications (McGraw-Hill, New York,1962).l o G. L. Pratt and D. Rogers, J.C.S. Faraday I, 1976,72,2764.l 1 S. W. Benson, Thermochemical Kinetics (Wiley, New York, 1968).j 2 L. Haar, J. C. Bradley and A. S. Friedman, J. Res. Nat. Bur. Stand., 1955,55,285.G. S. Bahn, Reaction Rate Compilation for the H-0-Nsystem (Gordon and Breach, New York,1968).l 4 H. S. Johnston, Gas Phase Reaction Rate Theory (Ronald, New York, 1966).l5 N. L. Arthur and J. A. McDonell, J. Chem. P h j ~ . , 1972, 56, 3100.(PAPER 6/983

ISSN:0300-9599    

DOI:10.1039/F19777300054

出版商:RSC    

年代:1977

数据来源: RSC

摘要:

Structure and Catalytic Activity of Iron Oxide andMagnesium Oxide Solid SolutionsPart 3.-E.S.R. CharacterizationB Y DANTE CORDISCHI, FRANCO PEPE, MARIO SCHIAVELLO AND MARIO VALIGICentro di Studio su “ Struttura ed attivitii catalitica di sistemi di ossidi ”,Istituto Chimico, University of Rome, Rome, ItalyandIstituto di Chimica Generale, University of Rome, Rome, ItalyReceived 3rd June, 1976Magnesium oxide + iron oxide, fired both in air and in a reducing atmosphere, and magnesiumoxide+iron oxideflithium oxide (up to 1 % atomic Fe) were investigated by e.s.r. spectroscopy.The effects of outgassing at various temperatures and of NzO decomposition on the e.s.r. spectraare discussed in terms of surface redox processes. The incipient formation of the spinel phase,MgFe204, and its precipitation, at the highest outgassing temperatures adopted, were readily studiedby the e.s.r.technique.The hypotheses previously proposed on the modification of the catalyst solid state, occurringduring N20 decomposition andlor in the vacuum treatment, are confirmed by the present study.Further details are also given.Electron spin resonance (e.s.r.) spectroscopy, which is commonly used for charac-terizing polycrystalline materials,l is also, due to its great sensitivity, a useful tool inthe field of heterogeneous catalysis, particularly when the catalyst is chemically alteredduring the course of the catalytic reaction. An example is the CuO + MgO systemin which e.s.r. results have been correlated with the catalytic activity for N20 de-corn posit ion.In this paper we report the results of an investigation on the system magnesiumoxide+iron oxide, fired in air or in a reducing atmosphere, and on the system mag-nesium oxide + iron oxide + lithium oxide.The structure and the catalytic propertiesfor N20 decomposition of such systems have been investigated previously,3* asolid state process being observed during the conditioning and catalytic procedures.The aim of this study was, therefore, to obtain a more detailed description of thesystem and to test the validity of some hypotheses proposed for the course of thecatalytic process. For these reasons the e.s.r. measurements were performed on the“ as prepared ” specimens as well as in conditions simulating the catalytic ones.EXPERIMENTALMATERIALSThe samples containing only iron were prepared by calcination of “ Specpure ” MgO(Johnson-Matthey) impregnated with Fe(NO,), solution at 1273 K for 5 h, in an oxidizing(air) or reducing (COz+ CO mixture giving an oxygen partial pressure of 1 .O x lo-’ N m-2)atmosphere, For samples containing both iron and lithium, a LiN0, solution was also6D.CORDISCHI, F. PEPE, M. SCHIAVELLO AND M. VALIGI 63added in the impregnation step ; they were fired at 1273 K for 5 h in air. Details of samplepreparation have been reported previ~usly.~Samples containing only iron are labelled MF and MF-R if prepared in air or in a reduc-ing atmosphere, respectively. Those also containing lithium are designated MFL. Thenumbers after the letters give the nominal concentration of iron and lithium with respect to100 Mg atoms.MgFe204 was prepared from MgO (from the carbonate decomposed in air at 873 K)impregnated with Fe(NO& solution in the correct stoichiometric ratio. The product wasfired in air at 1273 K for 5 h and cooled rapidly to room temperature.The formation and purity of the ferrite phase was tested by X-ray analysis.TREATMENTSA portion of the sample (0.1-0.3 g) was enclosed in a silica ampoule, having a standarde.s.r.tube as a side arm, connected to a vacuum system via a ground joint and isolated bymeans of a stop-cock. Treatments consisted of cycles of outgassing and subsequent N20addition. The N20 was added at 8000Nm-2 (60Torr) with the sample maintained at723 K ; outgassing was performed at various temperatures starting from 753 K.After each treatment the powder was transferred to the e.s.r.tube for measurements.E . S . R . PROCEDUREThe e.s.r. spectra were recorded at X-band frequencies on a Varian E-9 spectrometer atroom temperature or, occasionally, at 77 K.The absolute concentration of Fe3f ions was obtained by measuring the area under spectraintegrated electronically over 4000 G, using a single crystal of CuS04 5H20 as a standard.RESULTS AND DISCUSSIONSPECTROSCOPIC CHARACTERIZATION OF UNTREATED SAMPLESSAMPLES CONTAINING IRON ONLY FIRED I N AIR (MF)As reported previously this system contains two phases, MgO and the ferromag-netic MgFe,O,.Ferromagnetic resonance in powdered samples has been studied in only a fewcases,1 mainly due to the fact that the resonance field depends on crystal orientationas well as on the shape and porosity of the specimen.The purpose of the present investigation is not the study of the ferromagneticresonance of the ferrite, but rather the use of e.s.r.to detect the presence of thisphase.The e.s.r. spectra of the MF samples are very similar to those of the pure MgFe,O,[fig. l(a), (b), (c)] and to the calculated 0nes.l The main spectral feature of thesesamples is a very strong and broad signal whose line-shape varies slightly with sample,the amount of powder and the microwave power. Nevertheless, the overall linewidth (AH,,) at room temperature is fairly constant (800-1000 G). At 77 K abroadening by a factor of two occurs.The intensity of this signal is roughly pro-portional to total iron content but is so high that, with the exception of the mostdiluted samples (MF O.l), it obscures all other signals. Thus, due to the very strongintensity and in spite of the very broad linewidth, the ferrite phase can be detectedeasily by e.s.r. in very dilute samples (MF 0.1) in which X-ray investigation failed todetect it or in samples (with lithia, see below) in which this phase is present as a minorcomponent.The spectrum of the most dilute sample (MF 0.1) also shows a signal due toFe3+ ions in solid solution in MgO. The spectral feature of this signal will be describedbelow64 E.S.R. OF2000 3000 4000 5000HIGFIG. 1IRON OXIDE' 2000 3000 4000 500dHIGFIG.2FIG. 1.-X-band e.s.r. spectra at room temperature of untreated samples of (a) MF 0.5 ; (b) MF 1 ;(c) MgFez04 ; (d) MFL 1 : 0.5 ; (e) MFL 0.05 : 0.5 ; (f) MFL 0.5 : 0.25 ; (9) MFL 1 : 5. The num-ber under each spectrum indicates the relative gain.FIG. 2.-A'-band e.s.r. spectra at room temperature of MF-R 0.5 after various treatments : (a) un-treated sample; (b) after the first vacuum treatment at 753 K (treatment no. 1 of fig. 3 and 4);(c) after vacuum at 823 K (treatment no. 13) ; (d) after vacuum at 873 K (treatment no. 15) ; (e) aftervacuum at 973 K (treatment no. 19). In spectra (a)-@) the signals from impurities MnZ+ and Cr3+are aIso present (narrow peaks). The number under each spectrum indicates the relative gain.SAMPLES CONTAINING BOTH IRON A N D LITHIUM FIRED I N AIR (MFL)In these samples Fe3+ and Li+ are in solid solution in MgO when the ratio [Li]/[Fe] 3 1 ; MgFe,O, is also present when [Li]/[Fe] < l.3 In all the samples with[Li)/[Fe] < 1 the strong band of the ferrite which dominates the e.s.r.spectrum ispresent. In the samples at [Li]/[Fe] = 0.5 [fig. l(d)] it is also present with an inten-sity of -20 % of that of the sample without lithia having the same iron content.As [Li]/[Fe) increases the other signal, observed only in the dilute MF samples(MF O.l), progressively increases in intensity. This is the same signal generallyobserved in commercial undoped MgO samples of normal purity, fired in air, in whichiron is the most common paramagnetic impurity.This signal can be assigned toFe3+ ions in solid solution in MgO. At low iron contents (0.05-0.1) and with [Li]/[Fe] > 1, this signal shows all its details [fig. l(e)]. It consists of a central line ofunresolved structure at g = 2.00 with several shoulders on each side. These shouldersare not normally observable in undoped samples containing iron at impurity level,because their intensity is lower by a factor of - 10 with respect to the central lineD. CORDISCHI, F . PEPE, M. SCHIAVELLO AND M . VALIGI 65The complex structure of the e.s.r. signal of the Fe3+ ion in powder samples ofMgO can be completely interpreted from the known parameters of the spin Hamilton-iaii of Fe3+ in MgO, obtained from a single crystal study (see Appendi~).~ Theresolution of the spectrum depends on several factors, such as total iron concentrationand [Li]/[Fe] ratio.In the less resolved spectra only the most intense shoulders areobservable [see fig. l(f), (g)]. However, the characteristic shape of the central peak,its linewidth and the presence of the shoulders are a clear indication of the presenceof Fe3+ ions in solid solution in MgO in sites of cubic symmetry. Since these featuresare visible in all MFL samples up to 1 % iron content (and in the most dilute MF),we conclude that isolated Fe3+ ions in sites of cubic symmetry are present in MgO.Table 1 reports the absolute Fe3+ concentrations, evaluated from integrated spec-tra, for all samples fired in air. In the same table the linewidths of the ‘‘ cubic ”central peak and of the ferrite signal (when present) are also reported.TABLE 1.-E.S.R.DATA OF MF AND MFL SAMPLES FIRED IN AIRsampleMF 0.1MF 0.5MF 1MgFeaO4MFL 0.05 : 0.05MFL 0.1 : 0.05MFL 0.1 : 0.1MFL 0.1 : 1MFL 0.5 : 0.25MFL 0.5: 0.5MFL 0.5 : 2.5MFL 1 : 0.5MFL 1 : 1MFL 1 : 5Fe3+ in solid solution Fe3+ as MgFezO4AHPP Fe+3 * AH,, %4545454545454748464760Yes 1100 100950 1001050 1001100 1000.05 - -Yes 880 200.080.10 - -Yes 940 200.33 - -0.55 -Yes 1040 200.52 - -0.91 - -I --a Fe*j ions per 100 M g atoms.The following points are relevant to these data :(a) When the ferrite signal is present no reliable quantitative evaluation of theFe3+ concentration is possible, only the presence of the cubic signal being indicated.In all MF samples it has been assumed that all Fe3+ is present as ferrite.In theMFL samples in which the ferrite signal is present, the ferrite content has been roughlyestimated from the intensity of its signal relative to that of the corresponding MFsample.(b) In the MFL samples, the ferrite signal is absent only when the ratio [Li]/[Fe] 2 1. Only in the samples with [Li]/[Fe] > 1 does the Fe3+ concentration,(estimated error -20 %) agree with the nominal values. Since from analytical andmagnetic data,3 all iron is present as Fe3+ in the air-fired samples, when the [Li]/[Fe] = 1 some Fe3+ ions escape e.s.r. detection. Probably these ions are near to, or on, thesurface, giving a very broad signal because of the large anisotropic interactions.These results show that firing at 1273 K in air induces a uniform distribution ofFe3+ in the MgO matrix only when a large excess of Li+ is present.1-66 E.S.R.OF IRON OXIDESAMPLES CONTAINING IRON FIRED I N REDUCING ATMOSPHERE (MF-R)Previous results have shown that samples without lithia, prepared in a reducingatmosphere (CO+CO,) at 1273 K, (MF-R), were solid solutions with the iron inthe Fe2+ oxidation ~ t a t e . ~ Their e.s.r. spectra show the signal of “cubic” Fe3+ions, which is of low intensity. In addition, signals due to Mn2+ and Cr3+, presentas impurities in the MgO used, are observed [fig. 2(a)]. The intensity of the “ cubic ”Fe3+ signal is independent of the total iron content and corresponds to a smallfraction of the total iron present.The previous results are thus ~onfirrned,~ the Fe3+ content being well under thelimit of sensitivity of the analytical method.Also, at room temperature only Fe3+can be detected by e.s.r., whereas Fez+ (a d6 ion) can be seen in MgO only at liquidhelium temperatures, because of its short relaxation time.6EFFECTS OF TREATMENTS I N VACUO AND/OR IN N,QM F AND MFL SAMPLESThe treatments in vacuo and in N20 carried out on MF and MFL samples, pre-pared in oxidizing conditions, were as follows. The MF 0.5 specimen was treatedin vacuo at 753 K for 5 h, then in an N,O atmosphere (723 K ; P = 8000 N rn-,).The cycle was repeated and finally the specimen was outgassed at 923 K.The specimens MFL 1 : 0.5, MFL 0.1 : 0.05, MFL 0.1 : 0.1 and MFL 0.1 : 1 wereoutgassed at 873 K, exposed to NzO (723 K, P = 8000 N m-2) and finally evacuatedat 973 K.In general all these treatments have a small effect on the e.s.r.spectrum of oxidizedsamples. In particular vacuum treatment at the highest temperatures tested (923 K)causes small variations in lineshape of the ferrite signal (when present) without affect-ing its intensity. The effect of the treatments on the “ cubic ” signal is negligible inspecimens with [Li]/[Fe] 2 1 and is small and rather erratic in those with [Li]/[Fe] < 1.MF-R SAMPLESThe effect of treatments is quite large on reduced samples (MF-R). In generalthe vacuum treatment causes a decrease in the intensity of the “ cubic ” Fe3+ signal,while the N,O treatment causes an increase.The vacuum-N,O cycle was repeatedseveral times on the same sample, progressively increasing the temperature of thevacuum treatment but maintaining a constant temperature (723 K) for the N 2 0treatment. Fig. 3 shows the variation of the cubic Fe3+ signal intensity, evaluatedfrom the height of the central peak. When the temperature of the vacuum treatmentis relatively low (753 K) the main effect on the e.s.r. spectrum is a variation in intensity,without any significant alteration in the resolution [fig. 2(b)]. The concentration ofFe3+ evaluated from the integrated spectrum, remains rather low (a few percent oftotal iron) (fig. 4).Increasing the temperature of the vacuum treatment to 823 K provokes largervariations of the cubic signal intensity in the vacuum-N20 cycle (fig.3) and theappearance of another broad signal (AH,, - 120 G), which becomes progressivelymore intense [fig. 2(c)]. For vacuum treatment at 873 K this signal dominates thespectrum [fig. 2(d)]. The concentration of Fe3+ from the integrated spectrum nowcorresponds to a large fraction (up to 100 %) of the total ironD. CORDISCHI, F. PEPE, M. SCHIAVELLO AND M. VALIGII67+.-.- 753K -i823K+1 , 1 , , , 1 , 1 , , , , , , t0 4 8 12 16treatment numberFIG. 3.-Intensity of the central cubic peak (from first derivative spectra) of the samples MF-R 0.5(- - - -) and MFR 1 (-) after 0, 0 NzO treatment at 723 K, 4 h ; @, vacuum treatmentfor 12 h at the temperatures indicated.I7 4 II9 73 K-rnIIIIIII+ 753 K-----r-l 4823 K+ lw873 K H/8- - ./u,n-.- -&n-m- - - - -I 0-s0 4 8 12 16 20treatment numberFIG.4.-Integrated intensity of MF-R 0.5, after various treatments : the meaning of the symbols isthe same as for fig. 3.I l l l l r , l l l , l l , , , 68 E.S.R. OF IRON OXIDEThe largest variations in the intensity of this broad signal occur after the firstvacuum treatment at a higher temperature. In contrast to the behaviour of the*‘ cubic ” signal, the broad signal is insensitive to the subsequent N 2 0 treatment.By increasing the temperature of the vacuum treatment to 973 K the e.s.r. spn d r u mbecomes very intense and is similar to that of the MF samples ; it is, as discussed be-fore, assigned to the phase MgFe204.The ferrite phase has, in fact, been detccted’oy X-ray analysis of these samples at the end of the treatments.In a different set of treatments on the same samples (MF-R 0.5 and MF-R I),starting from 823 K (instead of 753 K as in the experiments of fig. 3) for the firstvacuum treatment, the broad signal develops only after the vacuum treatment at873 K and has an intensity an order of magnitude lower. Therefore, the repzatedvacuum-N,O cycles at 753 K not only cause reversible variations in intensity of thecubic Fe3+ sigiial (fig. 3), but also appear to assist the subsequent irreversiblc forma-tion of the broad signal.This broad signal can be assigned to associated Fe3+ ions in the ferrite phase. Theincrease in intensity of this signal does not indicate only the progressive oxidationof Fe2+ ions, but mainly the ordering of the Fe3+ ions into the ferrite phase.Infact, the intensity of the broad signal increases after the vacuum treatments and notafter the N20 treatments (fig. 4).When the temperature of the vacuum treatment is relatively low (up to 873 K),the mobility of ions and vacancies is very limited and the ferrite phase is rather dis-ordered and with extremely small particles. Only at 973 K is the ferrite well formed.These conclusions are in agreement with the results on diluted samples sintered in airat high temperature (1673 K) in which a large fraction of iron is in solid solution inMgO as Fe3+.’*CONCLUSIONThe results of the e.s.r. study confirm those previously obtained 3 9 and providefurther details.The MF system, in which the Fe3+ ions are almost completely present as MgFe204,was found to be rather inactive for N20 decomy~sition.~ Its inactivity was attributedto the difficulty of Fe2+ ion formation, the presence of which is essential for thecatalytic reaction to occur.The e.s.r. results confirm the resistance to reduction ofFe3+ ions in the ferrite phase.For the MF-R system, the highest activity was found for the same reactio!~.~The activity was attributed to the presence of Fe2+ ions which, during N,O decorn-position, were found to oxidize to Fe3+. In the subsequent outgassing treatment,the Fez+ ions were restored on the surface while the structure of the ferrite phasebuilt up.At the highest temperatures used, precipitation of the ferrite phase wasobserved. All these findings are consistent with the results of the present work.For the MFL system with [Li]/[Fe] > 1, the low activity was attributed to the diffi-culty of reducing Fe3+ ions in MgO and in the presence of excess Li20.4 This isfully confirmed ir, this study since the “ cubic ” Fe3+ signal is not affected appreciablyby the treatments simulating the catalytic conditiom.The high activity of the MFL specimens with [Li]/[Fe] < 1 was ascribed to thereduction of Fe3+ ions in MgO, the outgassing process causing lithium oxide loss fromthe latticee4 However, the expected decrease in the cubic Fe3+ signal was not alwaysobserved in e.s.r. measurements. The erratic behaviour of the intensity variationin this case does not allow any definite conclusions to be drawnD.CORDISCHI, F. PEPE, M. SCHIAVELLO AND M. VALIGI 69APPENDIXTheiFe3+ ion in MgO has a high cubic zero field splitting (a = +205 x lo-' ~ m - ~ ) , 'which gives an angular dependence in cubic symmetry and a coiriplex powder spectrum.Being at X-band frequencies, la1 < gpH, the perturbation theory can be used to findthe resonance conditions for all the transitions. The formulae for allowed transitions(AM = & l), to second order, given by Abragam and Bl~aney,~ areU &3 c+ ++ liv = gPH+2pa+(2-9p+7p2)-15gPHwhere the parameter p is related to the cubic potential : *p = (l4+m4+n4-3) and2, m, n are direction cosines of the static magnetic field with respect to the cubic axes.The extreme values of p are + 1 along a (loo} axis and - 3 along <I 1 1> ; anotherstationary value is -$ along (01 1).As seen from formulae (l), the transition + 3 t-) - 3 depends on a only to secondorder, while in the other transitions a fbst order term is also present.The e.s.r.signals of a powder sample in the normal first derivative presentation appear at fieldsat which a discontinuity in absorption occurs. This happens generally at the extremeand stationary values of the field for each transition.Lineshape calculations of the " central peak " have been reported previously. *For this transition the second order term gives the extreme values of the field at40 ar2 Hmin = HO- --27 Hofor p = - 3wherea hva ' = - and Ho = -SP SP'With the known values of a' = 219 G, g = 2.0037 and Ho = 3370 G (under ourexperimental conditions) we obtain AH = H,,, - Hmin = 45.0 G which is the observedwidth of the '' central peak ".For the other transitions, as the first order term, linear in p , is dominant withrespect to the second order term, the observed signals outside the central line willcorrespond merely to the extreme and stationary values of p .Without second ordercorrection the spectrum would show a symmetrical pattern ; the observed asymmetryis due to the second order effect.In table 2 the fields for the particular values of p , calculated from formulae (I),are reported. The calculated values agree quite well with the observed field positionsof the shoulders. As can be seen in fig. l(e), those belonging to +$ c+ -+ f transitionsare more intense than the corresponding ones belonging to -k3 f-) +$ transitions atldthe pair belonging to + 4 f-) ++, and p = - 3 is the most intense70 E.S.R. OF IRON OXIDETABLE 2.rALCULATED AND OBSERVED VALUES OF FIELD POSITION OF THE SHOULDERS OF E.S.R.SPECTRUM OF Fe3+ IN MgOP 1 1 -3 -3 -a -t -a -a -3 -+ 1 1transition-+*-* +%*+a ++u++ -*--+ +$c*+& -+w-s +Q.H+* -+--a +;-u+% -+-+ -++--3 ++u.Hce.10. 2818.3 2931.7 3015.3 3067.3 3220.5 3256.0 3475.0 3494.5 3651.6 3724.7 3808.3 3913.5Hobs. 2823 2935 3016 3066 3215 - - 3498 3645 3730 3800 3905The authors thank Prof. A. Cimino for valuable discussions and Dr. M. Petrerafor help given in some experiments.P. C. Taylor, J. F. Baugher and H. M. Kriz, Chem. Rev., 1975,75,203.D. Cordischi, F. Pepe and M. Schiavello, J. Phys. Chem., 1973,77, 1240.M. Valigi, F. Pepe and M. Schiavello, J.C.S. Faraday I, 1975, 71, 1631.M. Schiavello, M. Valigi and F. Pepe, J.C.S. Faraday Z, 1975, 71, 1642.W. Low, Proc. Phys. SOC. B, 1956,69, 1169.J. W. Orton, Electron Paramagnetic Resonance (Ilife Books, London, 1968), p. 200.G. P. Wirtz and M. E. Fine, J. Amer. Ceram. Soc., 1968, 51, 402.K. N. Woods and M. E. Fine, J. Amer. Ceram. SOC., 1969, 52,186.A. Abragam and B. Bleaney, EIectron Paramagnetic Resonance of Transition Ions (Clarendon,Oxford, 1970), p, 147.lo J. H. Lunsford, J. Chem. Phys., 1965,42,2617.(PAPER 6/1056

ISSN:0300-9599    

DOI:10.1039/F19777300062

出版商:RSC    

年代:1977

数据来源: RSC

摘要:

Nuclear Magnetic Relaxation of Alkali Halide Nuclei andPreferential Solvation in Methanol+ Water MixturesBY MANFRED HOLZ,* HERMANN WEINGARTNER AND HERMANN-GERHARD HERTZInstitut fur Physikalische Chemie und Elektrochemie der Universitat Karlsruhe,W. GermanyReceived 18th June, 1976Nuclear magnetic relaxation rates of the ionic nuclei 3JCl, 81Br, lz7I, 23Na and s7Rb in methanol+water mixtures have been measured over the complete mixture range and extrapolated to zerosalt concentration. The relaxation of all these nuclei is controlled by quadrupole interaction ; inthe theoretical part of this paper a formula is given which describes their relaxation behaviour inthe mixtures. In connection with these results a method is presented which uses the quadrupolarrelaxation studies as a source of information regarding preferential solvation and which yielded theresult that Na+ and Rb+ are preferentially hydrated whereas C1- and Br- are preferentially solvatedby methanol in the mixtures.These results are compared with those derived from chemical shiftmeasurements by other authors and the discrepancy, so revealed, for C1- (and Br-), is discussed.The nuclear magnetic relaxation of ionic nuclei possessing an electric quadrupolemoment, such as 35Cl, 79Br, *lBr, 1271, 23Na, gSRb, 87Rb, in aqueous and some non-aqueous solutions can be explained in terms of an electrostatic Given anunderstanding of quadrupolar relaxation in pure solvents, it should be possible toapply it to the study of the immediate environment of ions in mixed solvents.Accord-ingly in this paper we present relaxation rates for 35Cl, 81Br, 1271 and 23Na in theCH30H + H20 system, extrapolated to zero ion concentration over the completemixture range. The 87Rb data, published in ref. (6) were remeasured with a higheraccuracy, i.e., to lower salt concentrations. In the theoretical part of this paper aformula is given which well describes the relaxation behaviour of thc above nuclei ina mixed solvent.Although the problem of preferential or selective solvation has been studied bydifferent methods for many years,7 the n.m.r. studies play a specially important role,because thermodynamic methods for example suffer from the difficulty that it is inprinciple impossible to separate experimental thermodynamic quantities into valuesfor single ions, without using non-thermodynamic assumptions, whereas applying then.m.r.technique it is in principle possible to study (a) the resonance of nuclei residingon the different solvent species and (b) the resonance of the ionic nuclei in the electo-lyte. In favourable cases the resonance line of the solvent nuclei splits into separatedlines for " free '' and solvating molecules, allowing a direct determination of solvationnumbers, but unfortunately in most electrolyte solutions at room temperature onlyone resonance line is observed. Hitherto, n.m.r. studies of preferential solvation havemostly been concerned with solvent proton shifts [see e.g., literature cited in ref. (7)],though recently chemical shifts of alkali and halide ion nuclei have been reported 8-1[see also references (1)-(6) of ref.(S)].Besides chemical shift measurements, n.m.r. relaxation investigations may pro-vide information about preferential solvation in binary solvent mixtures. To our772 N.M.R. STUDIES OF SOLVATIONknowledge only a few attempts have been undertaken in this direction in the past. Thus,Frankel etaZ.12 utilized the strong effect of the paramagnetic Cr3+ ion on the transverserelaxation time of the solvent nuclei [some other papers, where the same method wasused, are reviewed in ref. (13)], whereas Craig and Richards l4 measured the 'Li spinlattice relaxation in dimethylformamide +water mixtures, though they did not findany indication that the Lis ion is specially linked with either solvent.In a previous87Wb relaxation study of RbF in methanol + water mixtures we found some evidencefor preferential solvation. Accordingly we tried to improve the applicable relaxationtechniques in order to investigate preferential solvation in detail, arguing that relaxa-tion techniques may not only complement the chemical shift methods, but in somecases be more successful. In a recently published paper l 5 we described a techniquewhich utilizes the intermolecular dipole-dipole relaxation rates of solvent protonscaused by the magnetic moments of the ionic nuclei. In contrast to the method de-scribed by Frankel et al." the ion in question must not have a strong paramagneticmoment ; therefore, the above mentioned method promises wider applicability.Specifically we note that since most alkali and halide ion nuclei possess a nuclearquadrupole moment, quadrupole relaxation may be especially suitable to investigatethe solvation properties of those ions.Furthermore, these nuclei often have verybroad resonance lines and difficulties arise if one applies chemical shift measurements.Quadrupole relaxation in such cases may lead to more reliable results.EXPERIMENTALRelaxation rate measurements of 3JCl, "Br, 1271 and 87Rb were performed as line-width measurements, using a Varian DP 60 spectrometer combined with an HR-8 PARlock-in amplifiery3~ 4 9 and an automatically controlled sweep switch. In some samples wemeasured Tl by pulsed n.m.r. and confirmed the equality of Tl and T2, thus establishingthe situation of " extreme narrowing ".Moreover, we measured in some samples the 79Brand 85Rb linewidths. The linewidth ratio of the different isotopes was found to be close tothe expected value.The 23Na spin lattice relaxation time measurements were made at 19 MHz with a BrukerSXP-4-100 pulse spectrometer. Here the low concentration data (0.2-1 mol kg-l) wereobtained using a signal averager.In every system we determined relaxation rates down to the lowest measurable concen-trations and then extrapolated the relaxation rates to zero salt concentration. In the case of35C1,81Br and 1271 we gauged the error of the extrapolation values to be + 10 %, whereasfor 23Na and 87Rb, + 5 % was estimated. In the case of 1271 at higher MeOH concentra-tions, the salt solubility limited the measurements, so the relaxation curve in fig.5 had to beextrapolated to values above 70 mol % MeOH. All substances were obtained from MerckA. G., Darmstadt. The salts were of " Suprapur " grade ; before use they were dried over-night at 100°C under vacuum. All systems were pre-pared by weighing the salt and the solvents. Samples containing I- ions were freed fromoxygen by the " freeze-and-pump " method. The sampIe temperature during all measure-ments was maintained constant at 25 & 0.5"C.Methanol was of " Uvasol " grade.RESULTSIn table 1 are reported the measured relaxation rates of 23Na, 87Rb, 35Cl, 81Brand 1271 as they depend on the salt concentration c in molality units (mol salt per1000 g solvent) and solvent composition. For some systems measurements were alsomade at other compositions, e.g., at 10, 50 or 90 mol % MeOH.These results fitsmoothly within the general pattern but are not given in table 1 . The extrapolatedlimiting relaxation rates at zero salt concentration (1/T1,2)&0 and (1 /T1,2)&eOH forthe two pure solvents are summarized in table 2. With exception of the 1271 valueM. HOLZ, H. WEINGARTNER AND H.-G. HERTZ 73the values for pure H20 are taken from our previous publications as indicated. ThelZ7I limiting relaxation rate in water, and all the values for pure MeOH given in table2, are determined from the measurements of this work.The 35Cl and 81Br limiting relaxation rates in MeOH are to be compared withextrapolated values which can be derived from relaxation data given in ref.(16).For 81Br one obtains a value (l/T2)KeOH = 11 0001: 1000 s-l which is in satisfactoryagreement with our result. In ref. (5) a value of (1/T2)LeOH = 300+40 s-l for 35ClTABLE 1 .-EXPERIMENTAL NUCLEAR MAGNETIC RELAXATION RATES IN THE MeOH+ H 2 0SYSTEM(1 IT1 tz)/s-1nucleus23Na87Rb35c1slBr1 2 7 1real t 1mol kg-11 .O NaBr0.8 NaBr0.6 NaBr0.4 NaBr0.2 NaBr1 .O RbF0.8 RbF0.6 RbF0.4 RbF0.2 RbF4.0 LiCl3.0 LiCl2.0 LiCl1 .O LiCl1.5 NaBr1.2 NaBr1 .O NaBr0.8 NaBr0.5 NaBr4.0 KI2.0 KI1.0 KI20mol %MeOH35.834.334.533.810901 0409859509023302602001606000512049454700440021 26018 15015 87040mol %MeOH51.349.049.346.11580148013201240124055042036030010 0108 7208 3308 0107 85036 00029 75028 52060mol %MeOH57.557.154.153.552.61780170016201590154070055043014 28012 80011 65011 50011 34039 85038 17080 mol %MeOH57.553.254.051 .O21 301 90017501680157070055017 80014 60013 60012 70012 20044 830100 inol "MeOH47.946.744.343421930182016601560145054564020 70015 54514 57013 50012 508TABLE 2.-RELAXATION RATES FOR INFINITE DILUTION IN NEAT WATER AND METHANOL,TOGETHER WITH kj = 7$/7zj VALUES AS TAKEN FROM REF.(25)nucleus (1 lTi,z)OHzO/S-1 ki ( 1 /T1,$'MeOH/s-l k23Na+ 16.2 1.4 41 2.5s7Rb;- 420 0.8 1380 1.635c1- 42 0.9 400 1.6* Br- 1050 0.7 11 750 1.54600 0.5 46 000 1.2 1271-was extrapolated from the data of ref.(16). In the present work we were able tomeasure down to lower concentrations and now find seemingly a more reliable valuewhich is higher by 33 %. Measurements at lower concentration lead also to highervalues for 23Na and 87Rb in MeOH, compared with those given in ref. (5): th743 Iv)1 nh" 1N . M . R . STUDIES OF SOLVATION-1 2tmol %MeOHFIG. l.--23Na magnetic relaxation rates extrapolated to zero salt concentration in MeOH+ H20mixtures (0). Dashed line : " theoretical " relaxation rates according to eqn. (6). x : 1 /T1 ' 0 1 /TO*values (right hand scale), ISP : isosolvation point. The straight line connects the two 1/Tl - 1 / ~ tvalues of the neat components and corresponds to the expected behaviour of 1 IT', 1 /TF for non-preferential solvation. For more details see text.mol % MeOHFIG.2.-*'Rb magnetic relaxation rates extrapolated to zero salt concentration in MeOHf HzOmixtures. All other details as given in fig. 1M. HOLZ, H. WEINGARTNER AND H.-G. HERTZ 75composition dependent *'Rb relaxation rates are also somewhat different as comparedwith ref. (6).In fig. 1-5 the solvent composition dependence of the limiting relaxation rates ofthe above mentioned nuclei are given as solid lines. If one tries to extrapolate the4.0-3.0- --- n c1HW N 4 20--FIG. 3.-"Cl':magneticFIG. 4.-*'Br magneticI nI , . , , ,' 20 ' 40 ' 60 ' 80 ' 100mol %MeOHrelaxation rate extrapolated to zero salt concentration in MeOH+ HzOmixtures.All other details as given in fig. 1.t Imol % MeOHrelaxation rates extrapolated to zero salt concentration in MeOH + H20mixtures. All other details as given in fig. 176 N.M.R. STUDIES OF SOLVATION*lBr and 35Cl relaxation rates given in ref (6) to infinite dilution, a roughly similarcomposition dependent curve to that shown in our fig. 3 and 4 is obtained, in spite ofthe reIatively great uncertainty of the data in ref. (6).ti;c!//j20 40 60 8'0 ' 100 ' t ; : : ; : : ; ' I 'mol % MeOHRG. 5.--"'I magnetic relaxation rates extrapolated to zero salt concentration in MeOH+ H 2 0mixtures. (In the range from 80 to 100 mol % MeOH no experimental data could be obtained.)All other details as given in fig.1.THEORETICALAccording to Abragani the nuclear quadrupole relaxation rate 1 /Tl in liquidsis given by an expression which has essentially the form- 1- = KiV:z~, (1)Tlwhere K , is a constant factor for a given nucleus i, is the mean squared electricfield gradient at the nucleus and z, is the correlation time for the nuclear quadrupoleinteraction describing the fluctuations of the field gradient. The electrostatic theoryof the relaxation of ionic nuclei possessing a quadrupole moment in electrolyte solu-tions has been developed by Valiev l8 and by one of the present auth0rs.l- 2 * l9Following this theory the electric field gradients in the solution arise from electricmom- and multipoles of neighbouring particles, i.e., from ion charges and solventdipoles.Changes in the environment of the ion, e.g., by changing the solvent com-position, should alter the field gradients and should therefore be reflected in thequadrupolar relaxation rate. To be sure that only ion-solvent interactions are caus-ing the relaxation rate, one has to exclude the ion-ion (ion-charge) contributions andso requires nuclear quadrupole relaxation rates extrapolated to infinite dilution of allionic species. We are then left with field gradients produced by electric dipoles of thesolvent molecules.The field gradient caused by a dipole m is proportional to m/r4 where r is the dis-tance between the solvent point dipole and the nucleus residing in the centre of thM.HOLZ, H . WEINGARTNER AND H.-G. HERTZ 77ion. Since the relaxation rate, which is proportional to the squared field gradient,depends upon r8, only the nearest neighbours of the ion contribute to the relaxation.This is why quadrupolar relaxation studies are especially suitable for the investigationof solvation phenomena.According to the theory l * 5 * 2o the relaxation rate produced by ni solvent dipolesinteracting with the quadrupole moment of a nucleus in the centre of an ion in a neatliquid is given aswith(1 + y,)2P2.I is the spin of the relaxing nucleus, Q its quadrupole moment, e is the charge of theproton, yco is the Sternheimer anti-shielding factor, P is a polarization factor, theprecise meaning of which has been given elsewhere,'.2o m2 is the mean square of theeffective electric dipole moment of the solvent molecule, which is given by the orienta-tion of the dipole moment relative to the vector ion-solvent molecule, g: = r;(l/r'}with 0.2 g8 6 1, is a factor which depends on the particular form of the radial partof the ion-solvent pair distribution function, g8 4 1 when the pair distribution func-tion is very sharp. T;O is the rotational correlation time of the vector connecting theion with the solvent molecule. (The superscript * indicates that the solvent moleculeis in the solvation sphere, whereas the superscript O in eqn (2) refers to quantities in aneat solvent.) A" = (I -e-6n) is a " quenching " factor which corrects for the factthat due to the symmetry effects, the field gradient may be rcduced or even vanish,if the n, dipoles are located near or at octahedral positions? [see e.g., ref.(20)].In a mixed solvent the solvation sphere of the ion of interest may be composedof i i i l molecules of the solvent 1 and of niz molecules of solvent 2. Thus we obtainwith nii+niz = n,, the total first coordination number of the ion i. The quantityA" takes account of the non-additivity of the symmetry quenching effect. Assumingthat the quantities Y ~ ~ , ~ and x2, which mainly determine the strength of the fieldgradient at the nucleus, do not differ very much in the mixture from those in the puresolvents, we can replace the unknown squared field gradients in the mixture by themeasured relaxation rates in the pure solvent (l/?'&, with j = 1, 2.Possible varia-tions of the radial part of the ion pair distribution function and possible variationsof the quenching behaviour in the mixture are taken into account by the quantities/lj = gajAj. Eqn ( 3 ) now gives :Here we introduce the relation izl = nio, = nF2, that is, we assume a constant solvationnumber (number of nearest neighbours) over the whole composition range 0 G x2 < 1(xj is the mole fraction of the componentjin the solvent mixture). For MeOH + H,Omixtures this assumption is supported by experimental results l5 and has also been-1 The lateral departure from cubic symmetry is represented by a distribution width parameter1.' A=O means strictly cubic symmetry; l+m means fully random lateral distribution of thesolvent dipoles in the solvation sphere78 N.M.R.STUDIES OF SOLVATIONused by other authors 21 who have investigated preferential solvation in this system.AS a consequence, it follows that we can replace in eqn (4) nil/nfi by xi1 and ~li2/ltio2by (1 -xi,) = x i 2 , xil and xi2 being the local mole fractions of the two componentsin the solvation sphere of the ion i. Now we establish the criterion that if the x i jdiffer from the macroscopic mole fractions x,, then we have " preferential solvation ".If we were not allowed to assume that ni is constant over the composition range, wewould have to know the composition dependence of ni/nf'l and n,/nio, in order to beable to determine selective solvation.In the special case, where the two correlation times zzl and T : ~ in a mixture may beregarded as equal, or if one introduces an averaged correlation time for both compo-nents, then we can write eqn (4) in the following form :which may be written in the formA* = A(al(xlxz +x&) + 3x:xzp+2x2x:[2(bz-bl)+(e2-el)l}z~--- - withal = 4(V1 + Y2)2 - 3( V2 -I- Y2)2 - (V, + Yl)2bl = (Vl+Y2)2; el = (Vl+Yl)2b2 = (V, + Y1)2 ; e2 = ( V2 + Y2)2p = 2 ( ~ ; + v;) 2- el - e2.In eqn (5a), A* has been written for a solvation complex which represents a tetra-hedron.Expressions for an octahedron may be developed in an analogous way.V i + Y j i = 1 , 2 ; j = 1,2is the field gradient at the ion nucleus produced by one solvent molecule of species i,and three solvent molecules of species j , all solvent molecules being in close contactwith the ion.V/ i = 1 , 2 ; i#jis the field gradient produced by two solvent molecules of species i.If in eqn (5b)the term in square brackets is zero, then A*/T: is a function symmetric with respectNow our procedure will be as follows. The quantities which occur on the righthand side of eqn (5) are divided into those which are measurable and those whichare not. The former are (l/Tl)F, (l/Tl);, and z:, the latter are p j / p j , j = 1,2 andA*. In a first approach we set p,/p; = 1, j = 1,2 and A* = 0. Then, knowingthe composition dependence of the correlation time 7: from other measurements suchas the deuteron relaxation times of the deuterated solvent molecules in the mixture,and measuring (l/Tl); and (l/Tl);, the timncated eqn ( 5 ) which now readsto x1 = x2 = 3M .HOLZ, H. WEINGARTNER AND H.-G. HERTZ 79allows us to predict the relaxation rate of an ionic nucleus in a mixed solvent underthe assumption of xl1 = xl, which corresponds to the absence of preferential solvation.Deviations of the experimentally determined composition dependence of 1 ITl fromthis " theoretical " or '' expected " curve may be interpreted in terms of preferentialsolvation or in terms of the neglect of the quantities pj/pj" and A*. In a subsequentdiscussion we try to decide which of the competing effects is dominant. If we formthe quantity l/Tl l/z: then in the case of non-preferential solvation we expect,according to eqn (6), a straight line between the two limiting values (l/TJ1 l/zz;and (1/Tl)2 l/zzi, each proportional to the squared electric field gradient in theappropriate neat component.This procedure is analogous to the chemical shiftmethod, where one also assumes that for non-preferential solvation a straight linemay be drawn between the chemical shift values in the two neat solvents. Then, aswith the chemical shift method, we can determine the so called " isosolvation point ".12EVALUATION AND DISCUSSIONThe correlation times 7: are connected with the rotational correlation times zcj(j = 1,2) of the polar solvate molecules in the pure (salt free) solvents. z,"~ of neatwater we know fairly well to be 2.5 ps.22 For methanol we use the rotational correla-tion time of the OD group z& = 4.4 ps [see ref.(91. Knowing the composition de-pendence of the deuteron relaxatioii rate (1 /Tl)D of the CH30D + D20 mixture 6 p 23s 24we are able to calculate an averaged z, for both coinponents in the following manner :7, = ~ , " l R,( 1 + 0.18~,) = 2.5 9 R,( 1 + 0.18~2) PS (7)withRD = (l/Tl)D/(l/Tl)~20 ; (l/Tl)&-, = deuteron relaxation rate in pure D20.The factor (1 +0.18x2) takes account of the fact that the rotational correlation timeof D20 in D20 is about 23 % longer than that of H20 in H20, whereas in methanolthe corresponding difference is only about 5 %. Given the correlation times in thesalt free solvent, we next have to calculate the correlation times in the first coordina-tion sphere which enter in eqn (6) and which we marked by a star. These correlationtimes differ from those in the " free " solvent.25 In ref. (25) the ratios z:;/zzj = k j ,j = 1,2 for the different ions in water and MeOH are given.(kj > 1 correspondsto a '' structure-promoting ", k j < 1 corresponds to a " structure-breaking " propertyof an ion in a solvent). The ratios for the mixed solvents, k,, are calculated for everyion by a linear interpolation between kl and k,. That such an approximation isquite reasonable can be seen from some experimental data in ref. (15). Thus weobtainT:? = kjTgj for the neat components j = 1,27: = k,z, for the mixed solvent.The k, values used are given in table 2, the 2, values are listed in table 3.TABLE 3.-ROTATIONAL CORRELATION TIMES IN THE MeOH+ HzO SYSTEM ACCORDING TOEQN (7)mol%MeOH 0 10 20 30 40 50 60 70 80 90 100Tc/PS 2.5 3.8 4.7 5.3 5.7 5.8 5.7 5.5 5.2 4.8 4.80 N .M . R . STUDIES OF SOLVATIONWith all these quantities in eqn (6) we can compare our experimental curves forthe relaxation rates with the " theoretical " or " expected " curves. In fig. 1-5 thedashed curves show this expected behaviour of the composition dependent relaxationrates. In all figures the quantities l/T1 l/zr plotted over the composition rangeare also given, showing more clearly which component is preferred in the solvationsphere of the corresponding ion, if selective solvation really occurs.In fig. 1 we see the results for Na+. The experimental curve shows the typicalmaximum, found for the first time for "Rb in MeOH+H20 mixtures.A similarmaximum was found in aqueous mixtures of dimcthylforniamide l4 and dimet hyl-sulphoxide 26 for the 7Li relaxation rates. This maximum is obviously caused by thebehaviour of the correlation time T:, since the calculated curve (dashed line) showsa maximum at almost the same composition of the solvent. The experimental curveshows higher relaxation rates than expccted for non-preferential solvation. Since(under the assumption of a constant first solvation number p i i = ny = n;) the fieldgradient in pure water is greater than in pure MeOH, this discrepancy between thetheoretical and experimental curves indicates preferential hydration of Na+ in MeOH+ H 2 0 mixtures. The I/Tl l / ~ : values reflect this behaviour more clearly, whenour treatment indicates an isosolvation point (ISP) for Na+ at about 87 moiMeOH.The discovery of preferential hydration for Na+ in MeOH + H 2 0 mixturesis in qualitative agreement with chemical shift measurements by Covington et a1.21In this case both methods lead to the sanie qualitative result.As seen in fig. 2 for s7Rb the experimental and calculated curves are almostidentical. Again the maximum appears at the same composition for both curves.This supports our assumption that the correlation times 7: used in the calculations,are well approximated. Unfortunately, as we see from the l/T1 I/T; values in thetwo neat liquids, the field gradient produced at the Rb+ centre by a water moleculeis, within experimental error, equal to the field gradient produced by a MeOHmolecule. In such a case coniplete preferential hydration, non-preferential solvationand complete preferential Folvation by MeOH lead to identical relaxation curves andthe three possibilities are indistinguishable.However, from the expected similarsolvation properties of Naf and Rb+, and from the results of our previous l 5 and afortlicoming paper,2 we conclude that the experimental curve for the quadrupolarrelaxation of s7Rb reflects preferential hydration.We now turn to anionic relaxation. The 1/T, l/z: values in fig. 3-5 show thatthe squared field gradients acting at the three halide ion nuclei in neat MeOH are2-3 times greater than in pure water. The characteristic maximum is no longer tobe seen.We also recognize that with Br- and C1- the expected curve lies below theexperimental one. In spite of the relatively large uncertainty of the experimentaldata, this result indicates preferential solvation by MeOH, with an isosolvation pointat about 30 mol % MeOH. For I- we find agreement between the two curves withinexperimental error, which means that the local mole fractions xil,z in the solvationsphere do not differ markedly from the macroscopic mole fractions x1 , 2 , correspond-ing in our treatment to the situation of non-preferential solvation. Thus, we arrivefor I- at the sanie result as with our intermolecular dipole-dipole relaxation s t ~ d y . ' ~Our result for C1-, on the other hand, contradict the result for CaCI, in H2Q+MeOH where with the Hittorf method preferential hydration for Ca2-and C1- was found.Moreover, Covington et aZ." analysed the 35Cl chemical shiftdata of Hall et al.' obtaining the result that Cl- is selectively hydrated in MeOH +H20. Also in Gordon's 29 book the paper of Hall et a l l 6 is cited as proof that Cl-and Br- are preferentially hydrated, in spite of the fact that Hall et ul. in their paperdid not draw this conclusion from their chemical shift data; on the contrary, thesM . HOLZ, H. WEINGARTNER AND H . - G . HERTZ 81authors pointed out that their relaxation data reported in the same payer appear torule out any preferential solvation of these halide ions.The Br- chemical shift data so far available are of insufficient accuracy ; thereforeCovington and co workers 21 were not able to give a detailed analysis yielding resultswhich could be compared with ours.However, one should expect that the Br-solvation properties lie between these of C1- and I-.In view of this situation we have to discuss possible sources of error in the evalua-tion of the relaxation results, especially those regarding the anionic nuclei, whichmay affect our conclusions.When proceeding from eqn (5) to eqn (6) we have set Pj/& = 1 and A* = 0. Inthe case of the anions, which are structure breaking in water, we do not suppose ahighly symmetric hydration sphere and, therefore, only negligible quenching of thefield gradient should occur, which means AT = 1. From our previous work weknow that in MeOH also one has to assume A; = 1 in order to be able to explainthe measured relaxation rates of the anionic nuclei.Thus it follows that no notice-able quenching effects are to be taken into account, which means that A* = 0 andPj = g j is a good approximation. From the entropies of solvation in MeOH com-pared with those in water, and also from the slowing down of the motion of the solventmolecules in the solvation sphere in MeOH, we are forced to conclude that in pureThere- MeOH one has a tighter packing around the anions, which means gQ2 > gal.fore, if Pj/@ is not constant, the only reasonable supposition is an increase of thisquantity in going from H20 to MeOH. If we vary pl/PT in a reasonable manner,e.g., from 1 to 2 or 3 and, correspondingly, p2/P2 from 0.5 or 0.33 to 1 (H20 -+ MeOH)then, using eqn (4), we obtain only a small deviation from the straight line for l/T111~: and no alteration of our conclusion for the anions.On the other hand, ourexperimental l/Tl l/z,* curve for Br- and Cl- may be fitted assuming a variation ofP1/Pf from 1 to 3 together now with a constant P2/p; = 1. This means, if we sup-pose only a sharpening of the water-ion radial pair distribution, that our conclusionmust be changed to " non-preferential solvation " for C1- and Br-. However, wefeel that we can rule out this last possibility, since it is hard to find any reason whyoniy onc component should reflect the structure changes in the mixture in its radialpair distribution function.In the case of the cations the increase of the gj/g;, if at all present, in going fromH 2 0 to MeOH, is then obviously accompanied by a decrease of Aj/Aj', since we find,e.g., for Na+ in MeOH a smaller field gradient, indicating that A; < A;.Thus, ifthe quantities pj/Pjo are not constant for the cations over the whole composition range,only small deviations are to be expected, and these would not alter our final con-clusions. However: it should not be overlooked that in the cationic case the quantityA* in eqn (5) may play a role. Since A*/z: is zero in the neat components, this quan-tity for the mixture has to go through a maximuin. Our experimental curve of1 /TI 1 /z,* for Rb+ shows no marked maximum, therefore A* seems to play only aminor role. With Na+ we cannot exclude a contribution of A':. Here our argumentis that in eqn (5b) e2-el is negative for 23Na and b2-bl is positive due to tightersolvent attachment of CH,OH, and one should expect a conipmsation of the quan-tities in the square brackets.Therefore A*/.tZ should give a symmetric contributionwith respect to x1 = x2 = 3, whereas our experimental results yield a curve which isdistinctly not symmetrical. As a consequence here too we believe that the A':'contribution is negligible and that our conclusion postulating preferential hydrationremains valid. In eqn (5) we introduced 7: instead of two different z:l and -* Lc2-We checked this point also and introduced different correlation times in eqn (4), asdetermined from some I7O quadrupolar relaxation data 3c) for MeOH and H,82 N.M.R.STUDIES OF SOLVATIONseparately. It turned out that our results are not markedly changed and, therefore,the use of one correlation time 7: in eqn (6) is legitimate.A further assumption inherent in our treatment was that the total solvation numberni is a constant over the whole composition range.It may be shown that the statement ni = const. has the following consequence :our local mole fractions characterizing preferential solvation retain their validity,however, the spatial extension of the first coordination sphere with respect to one ofthe components is an unknown function of the composition.In analogy toeqn (3) and ( 5 ) the chemical shift 6 may be written asIn conclusion we return to the discussion of the chemical shift.whereA6; = -nijgsj ' j 0 or Y,j = 1,2is the chemical shift of the ionic nuclear magnetic resonance frequency in the neatliquid j andThe chemical shift caused by one solvent molecule of species j depends on the ion-solvent separation as(V is unknown), and S* is the contribution due to non-additivity effects.The differencein the conclusions derived from relaxation and from chemical shift data may now easilybe traced as follows : if v M 8, then 6" should be < O in order to account for theobserved curvature convex towards the abscissa.16 On the other hand, if v 8,then the chemical shift senses solvent compositions which are further away from theion and the non-additivity contribution 6* may only be one part of the effect causingthe discrepancy between shift and relaxation results.It should be the purpose of future work, to clear up the existing discrepancy betweenthe chemical shift and the quadrupole relaxation results in the case of the anions.After having discussed the possible sources of error in the evaluation of our relaxationdata, we arrive at the result that there is indeed some evidence that Cl- and Br- arepreferentially solvated by MeOH.Finally, in connection with quadrupolar relaxation of ionic nuclei in mixed solventsystems, we point out that eqn (6) allows a good qualitative description of the relaxa-tion behaviour in a mixed solvent system for a number of different nuclei.This factshould encourage one to try to handle quadrupolar relaxation in other systems withthe same or a similar formula.H. G.Hertz, Ber. Bunsenges. Phys. Chem., 1973, 77, 531.H. G. Hertz, Ber. Bunsenges. Phys. Chem., 1973, 77, 688.H. G. Hertz, M. Holz, R. Klute, G. Stalidis and H. Versmold, Ber. Bunseitges. Phys. Chem.,1974, 78,24.H. G. Hertz, M. Holz, G. Keller, H. Versmold and C. Yoon, Ber. Bunsenges. Phys. Chem.,1974, 78, 493M. HOLZ, H. WEINGARTNER AND H.-G. HERTZ 83C. A. Melendres and H. G. Hertz, J. Chem. Phys., 1974, 61,4156.P. Neggia, M. Holz and H. G. Hertz, J. Chim. phys., 1974,71, 56.H. Schneider in Solute-Solvent Interactions, ed. J. F. Goetze and C. D. Ritchie (Marcel Dekker,New York, London, 1969), p. 301.J. P. Tong, C. H. Langford and T. R. Stengle, Canad. J. Chem., 1974,52,1721.A. K. Covington, I. R. Lantzke and J. M. Thain, J.C.S. Faraday I, 1974, 70, 1869.M. S. Greenberg and A. I. Popov, Spectrochim. Acta, 1975, 31A, 697.lo A. K. Covington and J. M. Thain, J.C.S. Faraday I, 1974,70,1879.l2 L. S. Frankel, C. H. Langford and T. R. Stengle, J. Phys. Chem., 1970,74,1376.l3 C. H. Langford and T. R. Stengle in N.M.R. of Paramagnetic Molecules ed. G. N. LaMar,W. Dew. Horrocks and R. H. Holm (Academic Press New York, 1973), p. 371.l4 R. A. Craig and R. E. Richards, Trans. Faraday Soc., 1963, 59, 1972.D. S. Gill, H. G. Hertz and R. Tutsch, J.C.S. Faraday I, 1976, 72, 1559.l6 C. Hall, G. L. Haller and R. E. Richards, Mol. Phys., 1969, 16, 377.A. Abragani, The Principles of Nuclear Magnetism (Oxford Univ. Press, London, 1961).l8 K. A. Valiev, Sov. Phys. J.E.T.P., 1960, 18, 77.l9 H. G. Hertz, 2. Elektrochem. Ber. Bunsenges. Phys. Chem., 1961, 65,20.‘O H. G. Hertz and M. Holz, J. Phys. Chem., 1974, 78, 1002.21 A. K. Covington, K. E. Newman and T. H. Lilley, J.C.S. Faraday I, 1973, 69,973.22 H. G. Hertz in Water, A Comprehensive Treatise, ed. F. Franks (Plenum Press, New York,23 E. v. Goldammer and H. G. Hertz, J. Phys. Chem., 1970, 74, 3734.24 E. v. Goldammer and M. D. Zeidler, Ber. Bzmsenges. Phys. Chepn., 1969, 73,4.25 G. Engel and H. G. Hertz, Ber. Bunsenges. Phys. Chem., 1968, 72, 808.26 A. I. Mishustin and Y. M. Kessler, J. Solution Chem., 1975, 4, 779.” M. Holz, J.C.S. Faraday I, in press ’* H. Schneider and H. Strehlow, 2. Elektrochem. Ber. Bunsenges. Phys. Chem,, 1962, 66,309.29 J. E. Gordon, The Organic Chemistry of Electrolyte Solutions (Wiley, New York, 1975), p. 257.30 C. J. Yoon, Thesis (Karlsruhe, 1974).London, 1973), vol. 3, p. 301.(PAPER 611 167

ISSN:0300-9599    

DOI:10.1039/F19777300071

出版商:RSC    

年代:1977

数据来源: RSC

摘要:

Desorption of Electrolytes at Liquid-Vapour andLiquid-Liquid InterfacesBY ROBERT AVEYARD," SYED M. SALEEM AND (IN PART) ROY HESELDENDepartment of Chemistry, The University of Hull, Hull HU6 7RXReceived 28th June, I976The desorption of various simple inorganic salts at the decanol-water interface has been studied,and analysed together with previously obtained results for the air-electrolyte and dodecane-electrolyte interfaces. The desorption of the salts is much more dependent on the nature of theanion, at all three interface types, than it is on the cation and the results are discussed in terms of thepossible interaction between anions and hydration layers at the interfaces. The dependence of freeenergies of adsorption of alkanols, both from alkane and from electrolyte, on the alkane-electrolyteinterface has also been investigated and it is concluded that the chemical potential of the alkanolat the surface is not much affected by the salts, but the influence is greater the less the desorption ofthe salt.In a recent paper we considered the effect of simple inorganic electrolytes on theinterfacial tensions of alkane-water interfaces. The work is extended here to includethe interface between decan- l-ol and aqueous electrolytes.In many systems where the behaviour of liquid-liquid interfaces plays animportant role (e.g., emulsions, micellar solutions, artificial lipid membranes inwater), it is quite common for electrolytes to be present.Although, unless a systemcontains ionic surfactant, inorganic salts may not have a drastic effect, it is clearlydesirable to have some knowledge of the magnitude of the effect, and, ideally, a nunderstanding of its origins.At a decanol-water interface it is likely that the polar groups of the alkanol areclosely packed.The influence of salts, present in the water, on such an interfacemight be relevant in, say, the investigation of changes in the critical micelle concentra-tions of non-ionic detergents when salts are added. On the other hand, the way inwhich isolated alkanol molecules (at say an alkane-water interface) respond to thepresence of salts might be different. We have, therefore, additionally studied theadsorption to the dodecane-electrolyte interface of (a) butan-1-01 from aqueousNaCl, and (b) dodecan- l-ol from n-dodecane.EXPERIMENTALInterfacial tensions were determined at 20°C using the drop-volume technique aspreviously described,2 and were reproducible to better than 0.05 mN m-'.The interfacial tension between decanol and water was independent of the length oftime the two phases were left in contact. Also, in experiments carried out with NaCl andKI it was found that no detectable amounts of salt (using standard titration techniques)were present in decanol which had been in contact with aqueous electrolyte for 24 h ormore. Further, there was no indication of transfer of any of the salts to the decaiiol duringthe interfacial tension measurements.In studying the adsorption of butanol from aqueous NaCl, account had to be taken ofthe distribution of the alcohol between the aqueous phase and dodecane.Prior to thedetermination of each interfacial tension, approximately 10 cm3 alkane and 100 cm3 aqueous8R. AVEYARD, S. M. SALEEM AND R. HESELDBN 85butanol were placed in a stoppered flask and shaken mechanically for two days in a waterthermostat maintained at 20fO.l"C. Since the distribution ratio for butanol is about 9(using molarity units) in favour of ~ a t e r , ~ the aqueous phase concentration was reduced byabout 1 % and an allowance was made for this. These necessary procedures rendered theresults a little less reproducible than those (see below) for the adsorption of dodecanol, andso very low butanol concentrations (i.e., less than about 3 x mol fraction), where inter-facial tension is a linear function of bulk concentration, were not studied.For the adsorption of dodecanol from solution in dodecane, no pre-equilibration betweenthe phases was necessary, and only bulk phase mole fractions of dodecanol up to about0 .7 ~ were used.Dodecane (Newton-Maine, purity > 99.5 %) was passed through chromatographicalumina prior to use. The decanol and dodecanol (Koch-Light, puriss), and butanol(Fluka, pztriss) had purities, as estimated by g.1.c. in this laboratory, of approximately99.3, 99.8 and 99.8 %, respectively. Water, taken from a laboratory still, was twicedistilled using all Pyrex glass apparatus. The samples of salt were the same as thosedescribed in ref. (1). In addition, BaCI2 (AnalaR grade) was used and was, like the othersalts, heated to 450°C for > 12 h in a silica crucible to remove organic impurities.RESULTSInterfacial tensions, yap, for decanol in contact with aqueous solutions of LiCl,NaCI, KC1, KBr, KI and BaCl, were determined at 20"C, and are given in table 1.All the salts except KI caused an increase in yap.TABLE 1 .-INTERFACIAL TENSIONS, yap, OF DECAN- 1 -OL AGAINST AQUEOUS ELECTROLYTESAT 20°Ceiectrolyte m,/mol kg-1 yaB/rnN m-1 electrolyte rn3lrnol kg-1 @/mN m-1NaCl 00.1230.2010.3430.5050.6650.81 30.9251.020KCl 0.2140.3950.6120.8381.146LiCl 0.1020.2040.3860.5970.7798.839.008.999.179.229.379.429.579.669.069.189.389.539.738.918.979.089.209.23KBr 0.2190.4190.6030.8421.025KI 0.2010.41 10.6220.8331.105BaClz 0.2010.4050.61 10.8210.9698.969.039.089.209.258.718.578 -458.368.299.089.259.479.669.83Results for the adsorption of dodecanol from dodecane to the interfaces withvarious electrolytes at 20°C are presented in table 2, as surface pressures, n, (thelowering of interfacial tension caused by adsorption) as a function of the mole fractionx of dodecanol in dodecane.For a given salt concentration n: and x are linearlyrelated. The surface pressures for butanol adsorbed from aqueous NaCl to theinterface with dodecane are listed in table 3. The mole fraction of butanol is definedas n(butanol)/[n(butanol) + n(water) + 2n(NaCI)], where the n are numbers of molesTABLE 2.-sURFACE PRESSURES, Z, FOR DODECAN-1-OL ADSORBED FROM DODECANE TO DODECANE-AQUEOUS1 0 4 ~ n/mN m-1dodecanol waterin dodecane0.082 0.140.105 0.170.207 0.350.212 0.310.302 0.450.364 0.540.425 0.710.480 0.700.683 1.010.688 1.04NaCl KC1 KBr K1m=1.020 m=2.082 m=1.031 m=2.129 m=1.038 m=2.157 m=1.050 m=2.2120.19 0.26 0.21 0.21 0.18 0.11 0.22 0.140.35 0.53 0.37 0.41 0.35 0.35 0.44 0.330.54 0.65 0.58 0.59 0.55 0.59 0.61 0.540.72 0.80 0.78 0.77 0.71 0.82 0.78 0.861.02 1.11 1.0s 1.09 1.03 1.03 1.11 1.0R .AVEYARD, S . M. SALEEM A N D R. HESELDBN 87TABLE 3.-sURFACE PRESSURES, IT, AND AQUEOUS PHASE MOLE FRACTIONy X , OF BUTAN-1-OLFOR ADSORPTION AT THE AQUEOUS NaC1-DODECANE INTERFACE AT 20°C1 0 4 ~1.031.401.892.643.323.794.324.625.00concentration of salt, m3/mol kg-10.78 ___--- 0 0.27 0.56nlmNm-1 10% n/mNm-’ lOlx n/rnNm-1 lO4x njmNm-12.45 0.33 1.21 0.29 1.15 0.28 1.623.10 0.55 1.84 0.57 1.83 0.60 2.653.81 0.85 2.47 0.89 2.64 0.88 3.255.10 1.11 2.W 1.15 3.20 1.13 3.856.02 1.41 3.59 1.83 4.62 1.83 5.316.57 2.04 4.73 2.11 5.09 2.12 5.867.21 2.29 5.42 2.49 5.78 2.40 6.417.57 2.84 5.95 2.98 6.68 3.01 7.547.911.14 -1 0 4 ~ n/mN m-10.27 1.820.52 2.430.79 3.051.05 3.941.39 4.712.21 6.512.51 7.162.76 7.60DISCUSSIONWe include data derived from previous results for electrolyte-air and electrolyte-dodecane interfaces,l as well as the present results for the electrolyte-decanolinterface.WORK OF ADHESIONOne possible way of expressing the effects of salts on material at interfaces is toexamine the work of adhesion, Wi@, between the organic phase, a, and the aqueouselectrolyte, phase p ; Wi@ is given bywhere y“ and y p are the surface tensions of a and p respectively.* In all the presentcases Wip varies in an apparently linear fashion with salt molality, m3, and can berepresented bywip = ya+yp-yae (1)where B is a constant and (Wip), is the work of adhesion of decanol or dodecane,with water.In the sense that B values, listed in table 4, are positive, the salts investi-gated can be said to “salt-in” both decanol and dodecane at the interface withTABLE 4.-vALUES OF B [EQN (2)] FOR THE WORK OF ADHESION OF DECAN-1-OL AND OFDODECANE WITH AQUEOUS ELECTROLYTES AT 20°CsaltLiClNaClKClKBrKIBaClzNa2S04BlmJ m-2 kg mol-1decanol dodecane1 .oo 0.020.94 0.290.82 0.220.96 0.501.74 1.311.93 -- 0.26* For the decanol-water systems, values of ya and yp for the non-mutually saturated liquids wereused.Values of fp for the saturated systems were not significantly different from (although morereproducible than) those obtained on initial contact of the two phases ; values quoted are for theequilibrium systems88 DESORPTION OF ELECTROLYTESaqueous electrolyte, the effect for a given electrolyte being greater for decanol thanfor dodecane. The changes are small, however. Suppose the area occupied by adecanol molecule at the interface is 0.20 nm2 (see later). Then, expressed per moleof decanol, the increase in Wib (for the decanol-electrolyte interface) caused by1 mol kg-1 NaCl is only 113 J mol-l, and by 1 mol kg-' BaClz is 230 J mol-'.The thermodynamic significance of Wif, and of the change, AWiB, caused by theaddition of salts to pure water, is not particularly simple, however. In general.y ina system of i components is given byY = A0-Z ripi ( 3 )iwhere A, is the specific excess interfacial Helmholtz free energy, Ti are surfaceexcesses, and pi are chemical potentials. It follows from eqn (1) and (3) that fortwo immiscible liquids, 1 (the sole component of phase a) and 2 (the solvent in phase p,which also contains the salt, component 3), Wifi is given byThe change, AWZp, is thuswhere it has been assumed that T;p is unchanged by the presence of salt, and I-';@ andI-'[ have been expressed relative to planes such that, respectively, I'gfi and are zero.Even this simplified expression for AWip contains a term for changes (denoted A)in A , caused by addition of salt, as well as a term in the difference in desorption ofsalt at the ap and interfaces.In a previous paper the contribution of the term inA, to AWip for the dodecane-electrolyte interface was estimated, crudely, by theuse of a theory of van der Waals forces.' In order to construct a simple physicalpicture of the nature of salt effects at interfaces, however, it is probably moreilluminating to consider values of F3 at the various types of interface.W f = A," + At - A",B + (qp- I';)pl + (I';p - r g ) p 2 + (r';B - r3p)p3.A W;P = A(AB, - A",B) + (ry - r , ~ ) ~ ,(4)(9ADSORPTION OF ELECTROLYTESFor the systems of present interest, in which liquids 1 and 2 are effectively im-miscible, and where the salt is soluble only in the water (liquid 2), it is readily shownthat the surface excess of salt, Tiz), relative to the plane where the surface excess ofwater, T,, is zero, is given byIn eqn ( 6 ) f k is the mean ionic molal activity coefficient of the electrolyte and v isthe number of moles of ions per mole of salt.As Ralston and Healy have pointedthe possibility exists that the planes corresponding to r2 = 0 may differ fordifferent concentrations of an electrolyte, and for different electrolytes. Thecomparisons of behaviour which follow are only as valid as is the assumption of aconstant I-', = 0 plane.In all cases y was observed to be a linear function of m3 f*, within experimentalerror.Activity coefficients were taken from the compilation in ref. (5) and are for2 5 T , but (in the present context) the coefficients for 20°C are very unlikely to besignificantly different. Values of for 1 in01 kg-' electrolytes are given in table 5.Ions are repelled by electrical image forces from an interface between aqueouselectrolyte and a second phase of low relative permittivity, E , . ~ , Further, it isbelieved that ions at the air-electrolyte interface can be attracted or repelled byforces associated with the hydration of ions and of the interface. Although E , fordecanol is 8 and that for dodecane -2, electrostatic theory [e.g., that of BellemansTi2) = - m,f~(dy/dm,f*)/vRT.(6R. AVEYARD, S . M . SALEEM AND R. HESELDEN 89referred to in more detail in ref. (l)] predicts only very minor differences in the eleva-t ion of interfacial tension for the systems of present interest. We therefore explorethe possibility that the trends in our results, as seen in table 5, are a consequence ofhydration effects.TABLE 5.-vALUES OF rp’ FOR 1 mOl kg-’ ELECTROLYTES AT 20°C ainterface LiCl NaCl KCI KBr KI BaCl2air /electrolyte 3.36 3.53 3.36 2.86 2.54 4.09C ,,H,,Jelectrolyte 3.02 2.95 2.91 1.80 -0.15 2.58CloH210M/electrolyte 1.23 1.57 1.63 0.84 -1.05 1.41a Values listed are of - lO’r~~/rnol m-’.In fig. 1, Ti2) for 1 mol kg-’ electrolytes is plotted against & I I , the entropychange which accompanies the formation of the outer hydration cosphere 9 9 lo ofthe appropriate ions.The desorption decreases, at all three interface types, as the‘‘ structure-breaking ” propensity of the anions increases (i.e., as Sx,Ir becomes morepositive); the desorption is much less dependent on the state of hydration of thecations. A similar plot is obtained if the free energy of ion hydration is substitutedfor Sx,Ir and the observed effects could be associated with the properties of eitherthe inner or the outer cosphere, or of course both. For a given salt the desorptionis least for the decanol-electrolyte interface and greatest for the air-electrolyteinterface.4 r-N IEI- 4 0 0 4 0 6 0SX,II/J mol-’ K-’FIG.1 .-Surface excess of salts in I rnolal solution as a function Of Sx.11. Curve 1, air-electrolyte ;curve 2, dodecane-electrolyte ; curve 3, decanol4ectrolyte. Ti’’ for LiCI, NaCl, and KCl (0) areplotted against SXJI for the cations ; rS2’ for KCI, KBr and KI (0) are plotted against S ~ , I L forthe anions.Less is understood about the structure of water at interfaces than about thehydration of ions. It is probable that the surface monolayer (at least) of water at theair-water surface is oriented such that on average the oxygen atoms point towardsthe vapour phase,’. “-14 although the extent of this orientation is not clear. None-theiess, the specific excess surface entropy, -dy/dT, for water is positive (0.26 mJm-2 K-I) suggesting that the structure over the whole interface is less extensive tha90 DESORPTION OF ELECTROLYTESin bulk.Good l4 has noted that the surface entropy of water is considerably morenegative than for many “normal” liquids, but this does not of course mean, asappears to be implied by Horne,15 that the surface structure is more extensive thanthat in bulk water.Both the enthalpy, AhiD, and the entropy, As:’, of adhesion for the dodecane-water interface and for the decanol-water interface are positive (table 6). If themajor contribution to Ahib and AsgP arises from changes associated with the structureof interfacial water, it may be inferred from the sign of the adhesion parameters thatwater at the air-water interface is less structured than that at either of the liquid-liquid interfaces.From the magnitude of the parameters it would appear that the“ randomness” of the interfacial water decreases in the orderair-wa ter > dodecane-water > decanol-water.TABLE 6.-VALUES OF (w~b)o, Ah:’, AND AS;’ FOR DECAN-1-OL-WATER AND DODECANE-WATERINTERFACES AT 20°Cdodecane-water decanol-water( Wib)o/mJ m-2 45.2 92.4AhIP ImJ m-2 92.4 182.6As;p/mJ m-2 K-I 0.16 0.31Values taken from ref. (16).The assertion that the enthalpy and entropy changes largely reflect changes in waterstructure has no claim to rigour, but it is supported to some extent by the observationthat the ratios of the free energies, of the enthalpies, and of the entropies, for thedodecane-water and decanol-water interfaces are very nearly equal (ie., 0.49, 0.51and 0.52 respectively).This implies that a similar process, taking place to differentextents, is responsible for the thermodynamic parameters of adhesion for the twointerface types; this could be the disruption of the structure of interfacial water.If so, it is noteworthy that, although decanol is capable of H-bond formation withwater and dodecane is not, the kind of structure involved is apparently similar(thermodynamically) in both cases.that, for the three interfaces of present interest, the halideions are desorbed less strongly than the metal ions. Thus, if the above argumentsabout interfacial water are accepted, it is concluded that the strongest attractionoccurs between the least strongly hydrated (i.e. greatest structure-breaking) anionsand the interfaces with the most strongly structured water.has, quiterightly, observed that for the air-water interface, the structure-breaking anions arein a region of relatively disordered water. We do not believe, however, that theattraction is a result of this disorder per se, but rather of the average orientation ofthe water molecules in such structuring as does exist. Indeed, it is possible that thewater at the decanol-water interface is more structured than bulk water since theentropy of interface formation (-dy“B/dT) is negative in this case. If the same kindof surface orientation as exists at the air-water surface is enhanced by the presenceof the organic phase, the anion-interface attraction would be correspondinglyenhanced, and the desorption reduced.Accepting that the hydrogen atoms of water molecules at the air-water surfacepoint on average into the liquid, it is understandable in a general way that anionsshould be attracted to the surface, and that cations should be repelled.From ourresults it appears that water molecules at the alkane-water and decanol-waterinterfaces are similarly oriented, but to a greater degree. What is less clear is why,for a given type of interface, the anion-interface attraction is greater the weaker theThere is evidence ‘*RandleR. AVEYARD, S . M. SALEEM A N D R . HESELDEN 91ion hydration. More specifically, it is not known if the effects arise from the natureof the outer or the inner cosphere, or from both. However, it is probable that thelayer of water molecules, separating the anions at the interface from the non-aqueousphase, is only one or possibly two molecules thick on average.l- It may be,therefore, that the oriented surface layer of water is directly adjacent to anions andhence acts as a partial, primary hydration sheath.Under these circumstances anion with a smaller primary hydration number in bulk (e.g., I-)2o would be attractedmore to the interface than an ion (e.g., Cl-) with a greater hydration number.Further speculation on the basis of the present results would be premature.Finally in this section we refer to the work of Ralston and Healy who foundthat the desorption of KCl (from a 3 mol dm-3 solution at 21°C) at the air+lectrolyteinterface is reduced by a factor of 2 when a close-packed monolayer of octadecan-1-01(area per molecule = 0.20 nm2) is spread at the interface.These findings areentirely consistent with our results for the desorption, from 1 mol kg-' KC1, at theair-electrolyte and decanol-electrolyte interfaces (table 5). The desorption in thepresence of the spread monolayer was found to be very dependent on the surfaceconcentration of the alkanol, which supports our earlier suggestion that the area perdecanol molecule at the interface is about 0.20 nm2.ADSORPTION OF ALKANOLSThe influence of salts on d h t e adsorbed films of alkanols has been investigatedin terms of the standard free energy of adsorption, AapO, of dodecan-1-01 from dilutesolution in dodecane to the interface with aqueous electrolyte.The free energy isgiven by 21A a p = - RT In (nlx) (7)where (n/x) is the slope of the linear plot of .n against x, obtained by least squarestreatment of the data in table 2. The standard state for the surface is n; = 1 mN m-',and for the bulk the state where the product of mole fraction and activity coefficientof the solute is unity. Since the salts used are insoluble in dodecane, the effect ofsalt on Aape arises entirely from changes in the standard chemical potential, p*sb,of alkanol at the interface. Further, we may reasonably assume that any observedeffects are predominantly associated with the OH group of the alkanol rather thanthe hydrocarbon chain.TABLE 7.-sTANDARD FREE ENERGIES OF ADSORPTION, A@*, OF DODECAN-1-OL FROM DODECANETO THE INflERFACE WITH AQUEOUS ELECTROLYTES, MOLALITY m3, AT 20°Csalt NaCl NaCl KCI KCI KBr KBr KI KIrn3/mol kg-l 1.020 2.082 1.031 2 .1 2 9 1.038 2.157 1.050 2.212-A@/kJmol-' 23.35 23.4, 23.45 23-50 23.39 23.56 23.52 23.61salt BaC12 BaClz CaC12 CaClzrn3/mol kg-l 1.033 1.578 1.030 2 . 1 1 4-Aa/.L*/kJ mol-' 23.66 23.91 23.68 24.24-Aa@ for adsorption at the dodecane-water interface is 23.42 kJ mol-I.It is difficult to assign precise errors to the values of Asp* given in table 7 ; thepresent value for adsorption to the alkane-water interface is about 1 % more negativethan a previously determined value,22 obtained using a different sample of dodecanol.We believe that for a given sample however, Aape values are reliable to better than0.1 kJ mol-I in a relative sense.On this basis it is seen that the 1 rnol kg-l (approx.92 DESORPTION OF ELECTROLYTES1,l electrolytes investigated have very little effect on Aape. At -2 mol kg-l theeffects are more discernable ; KCI, KBr and KI cause to be more negative(corresponding to “ salting-in ” of dodecanol at the interface) by about, respectively,0.08,0.14 and 0.19 kJ mol-l. We estimate from the results of Wilcox and S ~ h r i e r , ~ ~that the salting-in of the OH group in alkan-1-01s in bulk aqueous solution (at 25°C)by 2molkg-l NaC1, NaBr and NaI corresponds to changes in free energy of,respectively, about -0.34, -0.30 and -0.25 kJ mol-l. It appears then, that forelectrolytes that are strongly desorbed (e.g., alkali metal chlorides), the salt effect ORalcohol at the interface is less than that on the OH group in bulk.As the saltsbecome progressively less desorbed, the influence of salt on the solute at the interfacebecomes more pronounced and approaches the bulk behaviour. The magnitudeof the free energy changes is small, however, and the conclusions drawn are tentative.The effects caused by BaC1, and CaC1, are more substantial; in both cases thealkanol is salted-in at the interface. Any possible effects that may result fromchanges in the (very low) solubility of dodecanol in water as a result of salt additionhave been ignored in the above discussion.The change in A,p* caused by NaC1, for the adsorption of butan-1-01 fromaqueous electrolyte to the dodecane-water interface is substantial. In this case,however, the salt also influences the chemical potential, p*J, of butanol in bulksolution and we now proceed to show that, in fact, virtually all of the change inAsp* arises from this change in p*J.Since the adsorption was not studied in theconcentration range where n and x are linearly related, Aap* could not be calculatedfrom eqn (7) and was determined as follows. It is known 2 2 that adsorbed mono-layers of alkan-1-01s at alkane-water interfaces obey the Volmer equationin which a is the area per molecule of adsorbate at the interface and a, is the molecularco-area. The present data for butanol at the alkane-water interface have beenanalysed as described in ref. (22) and found to conform to eqn (8) with a.= 8.27 nm2molecule-l. We have assumed the same is true for films at the alkane-electroryteinterface and calculated a from n (table 3) using eqn (8). It has already been shownthat the effect of 1 molal NaCl on pego for dodecanol (table 7) is very small. Ifsuch changes as do occur involve mainly the OH group of the alkanol, we expect thechange in peso for butanol to be very small also. If this reasoning is sound, thechange in Aape should be almost equal to the change in p.9” caused by salt, whichquantity is known independently.n(a-ao) = kT (per molecule) (8)The adsorption isotherm corresponding to eqn (8) is l9a0 A a p v x=- a0 exp - exp (- - 1).a-a, a-a, RT (9)The adsorption free energy Aapesv is for a surface standard state of (ideal) halfcoverage (k, aoJa = 0.5), and is related to Asp* [eqn (7)] by 21AapOsV = Asp* - RT[ln (ao/kT) - 11.(10)TABLE 8 .-STANDARD FREE ENERGIES OF ADSORPTIONy Aape, OF BUTAN-1-OL FROM AQUEOUSNaCI, MOLALITY m3, TO THE INTERFACE WITH DODECANE AT 20°Cm3/mol kg-l 0 0.27 0.56 0.78 1.14-A,iCLe/kJ mol-l 24.88 25.23 25.43 25.80 25.98Sample plots according to eqn (9) are depicted in fig. 2 and the free energy ofadsorption, values of which are given in table 8, is a linear function of sodiuR . AVEYARD, S. M. SALEEM AND R . HESELDEN 93chloride concentration with dA,,@/dm, = -0.98 If: 0.10 (R.M.S. error) kJ inol-'/mol kg-l. On the above arguments dA,pe/dm, should be nearly equal to pOgl(butanol in water)--**' (butanol in 1 mol kg-l electrolyte), the mole fraction ofbutanol being the same in water and in electrolyte.The value for this difference inchemical potential obtained from distribution experiment^,^^ has been found to be- 1.07 kJ mol-'.FIG. 2.-Isotherms for adsorption of butanol from aqueous NaCl to the interface with dodecane at20°C. 0 , H20 ; m, 0.56 mol kg-' NaCl ; 0, 1.14 mol kg-l NaCI.SUMMARYThe salts studied cause an increase in the work of adhesion between water andboth dodecane and decanol, and in this sense can be said to salt-in these organicliquids at the electrolyte-liquid interface.It is suggested that trends observed in the desorption of salts are a result of inter-actions between anions and the hydration layers at the interfaces. The strongestattractive forces exist between interfaces with the most structured water, and thegreatest structure-breaking (i.e., least strongly hydrated) anions.The salts studied have only a small effect on the chemical potential of aikanolsadsorbed at the alkane-water interface. This is particularly true of salts which arestrongly desorbed. For less strongly desorbed salts, the effect on p e y b approachesthat which the salt has on the OH group in bulk aqueous solution.The effect of NaCl on the free energy of adsorption of butanol to the alkane-electrolyte interface is substantial and arises almost entirely as a result of the salting-out of alcohol from aqueous solution.The authors thank the S.R.C. for the provision of a postdoctoral maintenancegrant (Colloid Science) for S.M. S . , and Unilever Research, Port Sunlight, for astudentship for R. H.R. Aveyard and S. M. Saleem, J.C.S. Faraday I, 1976, 72, 1609.R. Aveyard and D. A. Haydon, Trans. Faraday Soc., 1965, 61,2255.R. Aveyard and R. W. Mitchell, Tram. Faraday SOC., 1969, 65, 264594 DESORPTION OF ELECTROLYTESJ. Ralston and T. W. Healy, J. Colloid Interface Sci., 1973, 42, 629.R. A. Robinson and R. H. Stokes, Electrolyte Solutions (Butterworth, London, 1955).J. E. B. Randles, Disc. Faraday SOC., 1957, 24, 194.B. E. Conway, J. Electroanalyt. Chem., 1975, 65,491.A. Bellemans, Physica, 1964, 30, 924.H. S. Frank and W. Y. Wen, Disc. Faraday SOC., 1957, 24, 133.London, 1973), vol. 3, p. 1.and Tobias (Interscience, N.Y., 1963), vol. 3, p. 1.lo H. L. Friedman and C. V. Krishnan, Water, A Comprehensive Treatise, ed. F. Franks Wlenum,l1 J. E. B. Randles, Advances in Electrochemistry and Electrochemical Engineering, ed. Delaheyl 2 H. J. M. Nedermeijer-Denessen and C. L. De Ligny, Electroanalyt. Chem., 1974, 57, 265.l 3 N. H. Fletcher, Phil. Mag., 1962, 7, 255.14R. J. Good, J. Phys. Chem., 1957, 61, 810.R. A. Horne in Water and Water Pollution Handbook, ed. Caccio (Dekker, N.Y., 1972),chap. 17 : see in particular fig. 18.l6 R. Aveyard, B. J. Briscoe and J. Chapman, J.C.S. Faraday I, 1972, 68, 10.l7 R. Lumry and S . Rajender, Biopolyrners, 1970, 9, 1125.l8 D. A. Haydon, Biochem. Biophys. Acta, 1961, 50,457.l9 K. Johansson and J. C. Eriksson, J. Colloid Interface Sci., 1974, 49, 469.*O J. O'M. Bockris and A. K. N. Reddy, Modern Electrochemistry (Plenum, N.Y., 1970), vol. 1,21 R. Aveyard and B. J. Briscoe, Trans. Faraday Soc., 1970, 66,2911.22 R. Aveyard and B. J. Briscoe, J.C.S. Faraday I, 1972, 68, 478.23 F. L. Wilcox and E. E. Schrier, J. Phys. Chem., 1971,75, 3757.24 R. Aveyard and R. Heselden, J.C.S. Faraday I, 1975, 71,312.p. 131.(PAPER 6/1238

ISSN:0300-9599    

DOI:10.1039/F19777300084

出版商:RSC    

年代:1977

数据来源: RSC

摘要:

Molecular Complexes of Substituted Aryl DiphenylmethylSulphides with n-AcceptorsCharge Transfer Spectra and Ionization Potentials of the DonorsBY GUSTAVO REICHENBACH,” SERGIO SANTINI AND G. GAETANO ALOISIIstituto di Chimica Fisica, Universit; di Perugia, 06100 Perugia, ItalyReceived 29th June, 1976Charge transfer complexes of substituted aryl diphenylmethyl sulphides, X1C6H4(X2C6H4)CH-S-C6H4Y, with tetracyanoethylene, 2,3-dichloro-5,6-dicyano-p-benzoquinone and chloranilhave been studied spectrophotometrically. The energy of the charge transfer transition is influencedby the substituents in Y, but is not affected by the substituents in X. The ionization potentialscalculated from the energy of charge transfer transitions are in good accord with those measured byphotoelectron spectroscopy.The nature of the donor orbitals is also discussed.It is known that the ionization potentials (i.p.) of electron-donor molecules maybe correlated with the charge transfer transition energy (hv,,) of complexes of thesemolecules with electron acceptor~.l-~ The empirical relation utilized is of the type :where the coefficients a and b depend only on the acceptor. On the basis of chargetransfer (c.t.) theory, a non-linear relationship between ijct and i.p. is predicted.Nevertheless, for chemically similar donors having i.p. values in a restricted range, theexperimental data lie on a virtually linear part of the curve, justifying the applicationof eqn (l).lm3 Many authors have used equations such as (1) for several types ofc.t.complexes to calculate the i.p. values of donors from their transition energieswith various acceptor^.^ We also have recently applied eqn (1) to c.t. complexesbetween aromatic and heteroaromatic sulphur derivatives (donors) and the n-acceptorschloranil (CHL), tetracyanoethylene (TCNE) and 2,3-dichloro-5,6-dicyano-p-benzo-quinone (DDQ).”’ The i.p. values estimated in this way were in good agreementwith those available by photoelectron (p.e.) spectroscopy.This study is now extended to c.t. complexes formed by a series of aryl-alkylsulphides (donors) and TCNE, DDQ and CHL (acceptors). In a previous work itwas reported that these donors interact with iodine (a-acceptor) to give mixed(n, n) + o* complexes in which the donation centre is localized on the sulphur atom.8The aim of this work is to extend knowledge of the energy and nature of the valencedonor orbitals interacting with the n acceptors, using the i.p.values obtainedempirically.i.p. = a+bvCt (1)EXPERIMENTALThe c.t. absorption spectra were studied for complexes of TCNE (Fluka AG purumgrade, recrystallized from chorobenzene and sublimed), DDQ and CHL (Fluka puriss.grade) with a large number of substituted aryl-alkyl sulphide donors in dichloromethane(Erba RP, purified following Vogel,’ dried and distilled). All the donors were availablefrom previous work.’996 MOLECULAR COMPLEXES OF SULPHIDESMeasurements were performed with a double-beam Optica CF4-DR spectrophotoineterwith a thermostatted cell compartment.Samples were prepared immediately beforemeasurement, the donor and acceptor concentrations ranging from 0.1 to 0.5 rnol dm-3 and2 x to 5 x mol dm-3, respectively.The pe. spectra were obtained with a Perkin-Elmer PS 18 photoelectron spectrometer.Reproducibility was & 0.05 eV.RESULTS AND DISCUSSIONThe spectral data for c.t. complexes formed between aryl-alkyl sulphides and.n acceptors are reported in table 1. The complexes with the acceptors TCNE andDDQ show two bands, although that at higher energy is not well resolved in theTABLE 1 .-CHA4RGE TRANSFER ABSORPTION MAXIMA FOR COMPLEXES OF SUBSTITUTED ARYLDIPHENYLMETHYL SULPHIDES, X1CsH40(2C6H4)CHSCsH~Y, AND SIMILAR COMPOUNDS WITHTCNE, CHL and DDQ IN DICHLOROMETHANE AT 20°Cl/nmX1HHHHHH4-Me4-C14-Ph4-Me4-C14-0MeMeSPhPhCH2SPhPh3CSPhx2HHHHHHHHH4-Me4-Cl4-OMeYH4-OMe4-Me4-c13-C14-FHHHHHHacceptor TCNE555,385600,380583,390525,370515,390510,380550,388540,380540,383560,390535,410 sh558,380575,380565,385530,395CHL480490510440435425460445465450440 sh485515500450 shDDQ*615 (450)690 (450)660 (450)610 (450)590 (460)610 (460)610 (450)605 (450)610605 (470)605630623 (445)565597 (455)* The second band is not well resolved.DDQ complexes, because its maximum is partially superimposed on that of theacceptor.Double bands for the c.t. complexes of TCNE and DDQ with t h i o p h e n ~ , ~ ~thioanisoles lo and diphenyl sulphides have recently been reported.They havebeen interpreted as due to transitions from two orbitals of the donor to the sameorbital of the acceptor. An analogous interpretation applies in the present case,in particular, the band at higher energy (second band) may be due to interactionbetween the acceptor molecule (TCNE or DDQ) and a more internal orbital of thethiyl group (see below). The lack of substituent effect in Y, in X1 and X" for thistransition (see table 1) is in agreement with the fact that the inner orbital which has u2symmetry is little affected by the substituent~.~~* l 1 For the CHL complexes, thesecond band has not been detected because, as expected from CHL electron affinity,6it falls at -300 nm, a region containing intense donor and acceptor absorption.With regard to the first band, some comments are in order. In fig.1 the energy ofthe first c.t. transition (vet) is plotted against the substituent constants opI2 accordingto a Hammett-type relation. The result shows that for donors substituted in Y theenergy of the transition is sensitive to the effect of substituents, and Vet increases withincrease in substituent constant 6, ( r = 0.982). The substituents in X1 and X2 haveno influence on the energy of the first band. This is in agreement with the suggestionG. REICHENBACH, S. SANTINI AND G. G. ALOISI 97reported previously,' that the band at lower energy is due to interaction between theTCNE (or other n-acceptor) and the outer anti-bonding orbital of the donor derivedfrom the sulphur-phenyl interaction, with a centre localized mainly on the sulphuratom.- 2.4 - 0.2 0 0 .2 0.4OPcircles represent derivatives substituted in Y, filled circles derivatives substituted in X.FIG. ].-Plot of the energy of the first c.t. transition against the op for TCNE complexes. OpenIn some sulphides, such as bis-4-methoxy-phenylmethyl phenyl sulphide, there is,indeed, evidence for a lower energy shoulder in the second band. This suggests thatit is a composite band. As for other examples in the literat~re,~ we suggest that theK N E interacts simultaneously with both parts of the molecule, i.e., with bothor,w C H - and thiyl part, S-giving rise to two isomeric complexes; consequently the band at higher energy isoriginated by two c.t.bands which overlap. This suggestion, which is also supportedby K,, measurement of complexes between TCNE and diphenylmethyl phenylsulphide, diphenyl methane and thioanisole,' may also be extended to the complexeswith the two other n-acceptors (CHL and DDQ).Table 2 lists the ionization potentials of the sulphides as calculated from Vct oftheir complexes with the various acceptors using eqn (1) in which a and b are asreported in ref. ( 5 ) and used in previous work. For some of the donors, the firsti.p. values were also determined experimentally by p.e. spectroscopy, the resultsbeing shown in the last column of table 2. The data in the table show that there isgood agreement between the experimental and calculated first ionization potentials.The exception is compound XV ; and the reason for this disagreement will be treatedbelow.Nevertheless, as also concluded elsewhere for other donors, it may beI--98 MOLECULAR COMPLEXES OF SULPHIDESaErmed that the empirically calculated i.p. values of table 2 represent reliable valuesand may even be considered good if compared with the experimental ones. Thesecond i.p. values reported in table 2 for TCNE were calculated from the maximumvalues of the second c.t. band. The separation between the two ionization energyvalues is of the same order of magnitude as that determined experimentally for thediphenyl ~u1phides.l~ This indicates that the second c.t. band originates from theinteraction between TCNE and a second inner n orbital of the thiyl group havingappropriate symmetry.TABLE 2.-IONIZATION POTENTIALS OF ARYL DIPHENYLMETHYL SULPHIDES, X1 CsH4(X2CsH4)CHSC6H4Y, AND SIMILAR COMPOUNDS AS OBTAINED FROM TRANSITION ENERGIES OF c.t.COMPLEXES WITH TCNE, CHL AND DDQ, AND FROM p.e.SPECTRAi .p . /eVdonor X1 X2 Y acceptor TCNE CHL DDQ p.e.HHHHHH4-Me4-Cl4-Ph4-Me4-OMe4-C1MeSPhPhCHzSPhPh3CSPhHHHHHHHH€34-Me4-C14-OMeH4-OMe4-Me4-C13 -C14-FHHHHHH8.18, 9.50 8.19 8.23 8.127.97,9.55 8.06 7.968.04,9.44 8.00 8.06 8.098.35,9.67 8.48 8.25 8.268.41,9.44 8.52 8.318.40, 9.55 8.60 8.338.21,9.46 8.36 8.258.27, 9.55 8.44 8.258.27, 9.52 8.29 8.278.21, 9.44 8.40 8.25 7.998.29,9.23 sh 8.48 sh 8.278.17, 9.55 8.15 8.278.09, 9.55 7.97 8.17 8.078.13, 9.50 8.06 8.20 8.008.32, 9.39 8.40 sh 8.45 7.97Fig.2 shows a plot of the p.e. ionization potentials of several diary1 and alkyl-arylsulphides as a function of the transition energy, vet, of their c.t. complexes with TCNE.The data, some of which have been taken from the literature, were obtained in thesame experimental conditions. Excluding the derivative Ph,C-S-Ph, the linearcorrelation obtained is reasonably good (Y = 0.991) and confirms that the donorcomplexes with TCNE are similar in nature. The deviation of Ph,C-S-Ph maybe ascribed to steric hindrance between the three phenyl groups and the reactioncentre, which alters the geometry of the complex since the TCNE is forced to lie farfrom the reaction centre.The presence of steric factors as a cause of substratedeviation from the reported relationship has been suggested previously. l4The linear correlation obtained fits the equation :i.p. = 1.63 x vCt + 5.19,which is in very good agreement with that obtained for mono- and poly-cyclicsubstituted benzenes, utilized in this and previous works to calculate the i.p. valuesof several aromatic sulphur derivatives, i.e. : i.p. = 1.65 x vCt + 5.21. Thisagreement confirms the correctness of the i.p. data obtained using the latter equationand also allows some conclusions to be drawn regarding the nature of the c.t. complexesbetween aromatic sulphides and n acceptors. It has been mentioned that, for agiven acceptor, the correlation is the same for donors of the same type.It is knownthat the outer donor orbital in aromatic sulphides is a R: orbital originating fromanti-bonding interaction between the sulphur atom and the adjacent phenyl groupG . REICHENBACH, S . SANTINI AND G. G. ALOISI9608.5->+ 3.I 8.07.599---I ! I I15 17 19 21 231 0-3 x &/cm-lFIG. 2.-Plot of the p.e. ionization potentials of diary1 and alkyl-aryl sulphides againstthe transition energy of their c.t. complexes with TCNE. The roman numerals refer to donors ofSMetable 2. The other compounds are : 1, 4a * 2, 4a psMe * 3,4=g5JgJSMe . 4, 4a MeSCHZPh. 5, PhSPh. 6, thiophen.'Consequently, when TCNE interacts with this orbital, a complex is formed which islittle different from that expected for typical n donors such as benzene and its deriva-tives.A difference between the two types of complexes may consist in the fact that,whilst for benzene the TCNE gives rise to a complex delocalized over the whole/\--5;.\molecule (03 , for aromatic sulphides, as the charge density is largely con-centrated on the S-C bond, TCNE interacts mainly with this zone, giving rise tocomplexes of the typesulphur atom., with the donor centre shifted towards theThe authors thank Dr. G. Distefano for the p.e. measurements100 MOLECULAR COMPLEXES OF SULPHIDESR. Foster, Nature, 1959, 183, 1253.R. Foster, Organic Charge Transfer Complexes (Academic Press, London, 1969).R. S. Mulliken and W. B. Person, Molecular Complexes: A Lecture and Reprint Volunte(Wiley, New York, 1969).See for instance (a) H. Bock, G . Wagner and J. Kroner, Chem. Ber., 1972, 105, 3850 ; (b) G.Wagner and H. Bock, Chem. Ber., 1974, 107, 68 ; (c) H. Bock and G. Wagner, TetrahedronLetters, 1971, 3713 ; (d) R. Locht, R. Cahay, J. Momigny and L. D’or, BulZ. Acad. roy. Belg.,1972, 58, 821.G. G. Aloisi and S. Pignataro, J.C.S. Faraday I, 1973, 69, 534.G. G. Aloisi, S. Santini and S. Sorriso, J.C.S. Faraday Z, 1974,70, 1908. ’ G. G. Aloisi, S. Santini and G. Savelli, J.C.S. Favaday Z, 1975, 71, 2045. * S. Santini, G. Reichenbach, S. Sorriso and A. Ceccon, J.C.S. Perkin IZ, 1974, 1056.A. I. Vogel, A Textbook of Practical Organic Chemistry (Longmans, London, 3rd edn., 1957),p. 173.A. D. Baker, D. P. May and D. W. Turner, J. Chem. SOC. B, 1968, 22 ; D. C. Frost, F. G.Herring, A. Katrib, C. A, McDowell and R. A. N. McLean, J. Phys. Chenz., 1972,76, 1030.l2 H. H. J a E , Chem. Rev., 1953, 53, 222.l3 F. P. Colonna, G . Distefano, G. Reichenbach and S. Santini, Z. Naturforsch., 1975,30a, 1213.i4 E. M. Voigt and C. Reid, J, Amer. Clrem. SOC., 1964, 86, 3930.lo A. Zweig, Tetrahedron Letters, 1964, 89.(PAPER 6/1259

ISSN:0300-9599    

DOI:10.1039/F19777300095

出版商:RSC    

年代:1977

数据来源: RSC