摘要:

Contents 3663 3669 3675 3683 3693 370 1 3709 3717 3725 3737 Normal and Abnormal Electron Spin Resonance Spectra of Low-spin Cobalt(r1) IN,]-Macrocyclic Complexes. A Means of Breaking the Co-C Bond in B12 Co-enzyme M. Green, J. Daniels and L. M. Engelhardt The Interaction between Superoxide Dismutase and Doxorubicin. An Electron Spin Resonance Approach V. Malatesta, F. Morazzoni, L. Pellicciari-Bollini and R. Scotti Biomolecular Dynamics and Electron Spin Resonance Spectra of Copper Complexes of Antitumour Agents in Solution. Part 2.-Rifamycins R. Basosi, R. Pogni, E. Tiezzi, W. E. Antholine and L. C. Moscinsky An Electron Spin Resonance Investigation of the Nature of the Complexes formed between Copper(I1) and Glycylhistidine D. B. McPhail and B. A. Goodman A Vibronic Coupling Approach for the Interpretation of the g-Value Temperature Dependence in Type-I Copper Proteins M.Bacci and S. Cannistr aro The Electron Spin Resonance Spectrum of Al[C,H,] in Hydrocarbon Matrices J. A. Howard, B. Mile, J. S. Tse and H. Morris N; and (CN); Spin-Lattice Relaxation in KCN Crystals H. J. Kalinowski and L. C. Scavarda do Carmo Single-crystal Proton ENDOR of the SO, Centre in y-Irradiated Sulphamic Acid N. M. Atherton, C. Oliva, E. J. Oliver and D. M. Wylie Single-crystal Electron Spin Resonance Studies on Radiation-produced Species in Ice 1,. Part 1.-The 0- Radicals Single-crystal Electron Spin Resonance Studies on Radiation-produced Species in Ice I,. Part 2.-The HO, Radicals J. Bednarek and A. Plonka J. Bednarek and A. PlonkaContents 3663 3669 3675 3683 3693 370 1 3709 3717 3725 3737 Normal and Abnormal Electron Spin Resonance Spectra of Low-spin Cobalt(r1) IN,]-Macrocyclic Complexes.A Means of Breaking the Co-C Bond in B12 Co-enzyme M. Green, J. Daniels and L. M. Engelhardt The Interaction between Superoxide Dismutase and Doxorubicin. An Electron Spin Resonance Approach V. Malatesta, F. Morazzoni, L. Pellicciari-Bollini and R. Scotti Biomolecular Dynamics and Electron Spin Resonance Spectra of Copper Complexes of Antitumour Agents in Solution. Part 2.-Rifamycins R. Basosi, R. Pogni, E. Tiezzi, W. E. Antholine and L. C. Moscinsky An Electron Spin Resonance Investigation of the Nature of the Complexes formed between Copper(I1) and Glycylhistidine D. B. McPhail and B. A. Goodman A Vibronic Coupling Approach for the Interpretation of the g-Value Temperature Dependence in Type-I Copper Proteins M. Bacci and S. Cannistr aro The Electron Spin Resonance Spectrum of Al[C,H,] in Hydrocarbon Matrices J. A. Howard, B. Mile, J. S. Tse and H. Morris N; and (CN); Spin-Lattice Relaxation in KCN Crystals H. J. Kalinowski and L. C. Scavarda do Carmo Single-crystal Proton ENDOR of the SO, Centre in y-Irradiated Sulphamic Acid N. M. Atherton, C. Oliva, E. J. Oliver and D. M. Wylie Single-crystal Electron Spin Resonance Studies on Radiation-produced Species in Ice 1,. Part 1.-The 0- Radicals Single-crystal Electron Spin Resonance Studies on Radiation-produced Species in Ice I,. Part 2.-The HO, Radicals J. Bednarek and A. Plonka J. Bednarek and A. Plonka

ISSN:0300-9599    

DOI:10.1039/F198783FX033

出版商:RSC    

年代:1987

数据来源: RSC

摘要:

Electrochemistry Group Workshop on Electrochemical Techniques and Instruments To be held at the University of Warwick on 6-7 January 1988 Further information from Dr P. N. Bartlett, Department of Chemistry, University of Warwick, Coventry CV4 7AL Surface Reactivity and Catalysis Group with the Process Technology Group and the Institute of Chemical Engineers Opportunities for Innovation in the Application of Catalysis To be held at Queen Mary College, London on 6-7 January 1988 Further information from Professor J. Pritchard, Queen Mary College, London Division with the Institute of Mathematics and its Applications Mathematical Modelling of Semiconductor Devices and Processes To be held at the University of Loughborough on 7-8 January 1988 Further information from the Institute of Mathematics, Maitland House, Warrior Square, Southend-on-Sea SS1 2JY Division London Symposium: Modern Electrochemical Systems To be held at Imperial College, London on 12 January 1988 Further information from Mrs Y.A. Fish, Royal Society of Chemistry, Burlington House, London W1V OBN Polymer Physics Group with the 3Ps Group Plastics, Packaging and Printing To be held at the Institute of Physics, 47 Belgrave Square, London on 18 February 1988 Further information from Dr M. Richardson, National Physical Laboratory, Teddington, Middlesex l w 1 1 OLW Theoretical Chemistry Group Postgraduate Students’ Meeting To be held at University College, London on 2 March 1988 Further information from Dr G. Doggett, Department of Chemistry, University of York, York Colloid and Interface Science Group with The Society of Chemical Industry and British Radio frequency Spectroscopy Group Spectroscopy in Colloid Science To be held at the University of Bristol on 5-7 April 1988 Further information from Dr R. Buscall, ICI Corporate Colloid Science Group, PO Box 11, The Heath, Runcorn WA7 40E Annual Congress: Division with Electrochemistry Group Solid State Materials in Electrochemistry To be held at the University of Kent, Canterbury on 12-15 April 1988 Further information from Dr J.F. Gibson, Royal Society of Chemistry, Burlington House, London W1V OBN Electrochemistry Group with The Society of Chemical Industry Electrolytic Bubbles To be held at Imperial College, London on 31 May 1988 Further information from Professor W. J. Albery, Department of Chemistry, Imperial College of Science and Technology, South Kensington, London SW7 2AY Electrochemistry Group with The Society of Chemical Industry Chlorine Symposium To be held at the Tara Hotel, London on 1-3 June 1988 Further information from Dr S.P. Tyfield, Central Electricity Generating Board, Berkeley Nuclear Laboratories, Berkeley, Gloucestershire GLI 3 9BP Gas Kinetics Group Xth International Symposium on Gas Kinetics To be held at University College, Swansea on 24-29 July 1988 Further information from Dr G. Hancock, Physical Chemistry Laboratory, South Parks Road, Oxford OX1 302 (xiii)Electrochemistry Group Workshop on Electrochemical Techniques and Instruments To be held at the University of Warwick on 6-7 January 1988 Further information from Dr P.N. Bartlett, Department of Chemistry, University of Warwick, Coventry CV4 7AL Surface Reactivity and Catalysis Group with the Process Technology Group and the Institute of Chemical Engineers Opportunities for Innovation in the Application of Catalysis To be held at Queen Mary College, London on 6-7 January 1988 Further information from Professor J. Pritchard, Queen Mary College, London Division with the Institute of Mathematics and its Applications Mathematical Modelling of Semiconductor Devices and Processes To be held at the University of Loughborough on 7-8 January 1988 Further information from the Institute of Mathematics, Maitland House, Warrior Square, Southend-on-Sea SS1 2JY Division London Symposium: Modern Electrochemical Systems To be held at Imperial College, London on 12 January 1988 Further information from Mrs Y.A. Fish, Royal Society of Chemistry, Burlington House, London W1V OBN Polymer Physics Group with the 3Ps Group Plastics, Packaging and Printing To be held at the Institute of Physics, 47 Belgrave Square, London on 18 February 1988 Further information from Dr M. Richardson, National Physical Laboratory, Teddington, Middlesex l w 1 1 OLW Theoretical Chemistry Group Postgraduate Students’ Meeting To be held at University College, London on 2 March 1988 Further information from Dr G. Doggett, Department of Chemistry, University of York, York Colloid and Interface Science Group with The Society of Chemical Industry and British Radio frequency Spectroscopy Group Spectroscopy in Colloid Science To be held at the University of Bristol on 5-7 April 1988 Further information from Dr R.Buscall, ICI Corporate Colloid Science Group, PO Box 11, The Heath, Runcorn WA7 40E Annual Congress: Division with Electrochemistry Group Solid State Materials in Electrochemistry To be held at the University of Kent, Canterbury on 12-15 April 1988 Further information from Dr J. F. Gibson, Royal Society of Chemistry, Burlington House, London W1V OBN Electrochemistry Group with The Society of Chemical Industry Electrolytic Bubbles To be held at Imperial College, London on 31 May 1988 Further information from Professor W. J. Albery, Department of Chemistry, Imperial College of Science and Technology, South Kensington, London SW7 2AY Electrochemistry Group with The Society of Chemical Industry Chlorine Symposium To be held at the Tara Hotel, London on 1-3 June 1988 Further information from Dr S. P. Tyfield, Central Electricity Generating Board, Berkeley Nuclear Laboratories, Berkeley, Gloucestershire GLI 3 9BP Gas Kinetics Group Xth International Symposium on Gas Kinetics To be held at University College, Swansea on 24-29 July 1988 Further information from Dr G. Hancock, Physical Chemistry Laboratory, South Parks Road, Oxford OX1 302 (xiii)

ISSN:0300-9599    

DOI:10.1039/F198783BX035

出版商:RSC    

年代:1987

数据来源: RSC

摘要:

ISSN 0300-9599 JCFTAR 83(9) 2693-3092 (1 987) JOURNAL OF THE CHEMICAL SOCIETY Faraday Transactions I Physical Chemistry in Condensed Phases 2693 2697 2705 2709 2719 2727 2735 275 1 2757 2765 2773 2787 2795 2803 2813 2825 2835 284 1 CONTENTS A New Pressure-programmed Volumetric Method of Measuring Adsorption at the Gas-Solid Interface D. I. Hall, V. A. Self and P. A. Sermon The Inclusion of Diflunisal by a- and P-Cyclodextrins. A 19F Nuclear Magnetic Resonance and Spectrophotometric Study) S. F. Lincoln, A. M. Hounslow, J. H. Coates and B. G. Doddridge Microcalorimetric Measurement of the Enthalpies of Transfer of a Series of ortho- and para-Alkoxyphenols from Water to Octan-1-01 and from Isotonic Solution to Escherichia coli Cells A. E. Beezer, M. C. P. Lima, G. G. FOX, P.Arriaga, W. H. Hunter and B. V. Smith The Vapour Pressure of Benzene. Part 1.-An Assessment of Some Vapour- pressure Equations The Vapour Pressure of Benzene. Part 2.-Saturated Vapour Pressures from 279 to 300 K P. D. Golding and W. D. Machin Comparison between Heterogeneous and Homogeneous Electron Transfer in p- Phenylenediamine Systems A. Kapturkiewicz and W. Jaenicke Kinetic and Equilibrium Studies associated with the Aggregation of Non-ionic Surfactants in Non-polar Solvents P. Jones, E. Wyn-Jones and G. J. T. Tiddy The Inclusion of Tropaeolin 000 No, 2 by Permethylated P-Clyclodextrin. A Kinetic and Equilibrium Study R. P. Villani, S. F. Lincoln and J. H. Coates C5emisorption and Disproportionation of Carbon Monoxide on Palladium/ Silica Catalysts of differing Percentage Metal Exposed C.L. M. Joyal and J. B. Butt Infrared Studies on Dinitrogen and Dihydrogen adsorbed over TiO, at Low Temperatures A Small-angle Neutron Scattering Investigation of Rod-like Micelles aligned by Shear Flow The Study of Aluminium Deposition from Tetrahydrofuran Solutions of AlCl,-LiAlH, using Microelectrodes. Part 1 .-1 : 1 AlC1,-LiAlH, J. N. Howarth and D. Pletcher The Study of Aluminium Deposition from Tetrahydrofuran Solutions of AlC1,-LiAlH, using Microelectrodes. Part 2.-The Influence of Solution Composition Electron Spin Resonance Studies of HPt(CN)i- and Pt(CN)i- formed by Irradiation of K,Pt(CN), in Solvents J. L. Wyatt, M. C. R. Symons and A. Hasegawa Medium Effect on the Electrochemical Behaviour of the CdlI/Cd (Hg) System in Propane- 1,2-diol-Water Mixtures R.M. Rodrigues, E. Brillas and J. A. Garrido Kinetic Modelling of Multiple-site Activity and the Kinetics of Inhibition Reactions in the Hydrogenolysis of C,H, on a Nickel Wire Catalyst S. Kristyan and R. B. Timmons Study of the Influence of the Impregnation Acidity on the Structure and Properties of Molybdena-Silica Catalysts H. M. Ismail, C. R. Theocharis and M. I. Zaki Electrochemical Properties of Cation Exchange Membranes A. D. Dimov and I. Alexandrova P. D. Golding and W. D. Machin Y. Sakata, N. Kinoshita, K. Domen and T. Onishi P. G. Cummins, E. Staples, J. B. Hayter and J. Penfold J. N. Howarth and D. Pletcher2847 2857 2867 2883 2895 290 1 2905 2913 2925 2935 2953 2963 2973 2985 2993 300 1 3015 3027 3039 Contents The Hydration of Aliphatic Aldehydes in Aqueous Micellar Solutions V-R.Hanke, W. Knoche and E. Dutkiewicz Ground-state Reduced Potential Curves (RPC) of Non-metallic First- and Second-row Hydrides F. JenZ and B. A. Brandt Hydrogen Bonding. Part 2.-Equilibrium Constants and Enthalpies of Complexation for 72 Monomeric Hydrogen-bond Acids with N-Methyl- pyrrolidinone in 1 1,l-Trichloroethane M. H. Abraham, P. P. Duce, J. J. Morris and P. J. Taylor Catalysis by Amorphous Metal Alloys. Part 6.-Factors controlling the Activity of Skeletal Nickel Catalysts prepared from Amorphous and Crystalline Ni-Zr Powder Alloys H. Yamashita, M. Yoshikawa, T. Funabiki and S. Yoshida Catalysis by Amorphous Metal Alloys. Part 7.-Formation of Fine Fe Particles on the Surface of an Alloy in the Recrystallisation State prepared from an Amorphous Fe,,,Zr,, Powder Alloy H.Yamashita, K. Sakai, T. Funabiki, S. Yoshida and Y. Isozumi Chemical Equilibria and Kinetics at Constant Pressure and at Constant Volume E. Whalley Cluster Size Distribution in a Monte Carlo Simulation of the Micellar Phase of an Amphiphile and Solvent Mixture Transformation of But- 1 -ene into Aromatic Hydrocarbons over ZSM-5 Zeolites Y. Ono, H. Kitagawa and Y. Sendoda Intermolecular Structure around Lithium Monovalent Cations in Molten LiAlC1, Y. Kameda and K. Ichikawa Excited-state Reactivity in a Series of Polymerization Photoinitiators based on the Acetophenone Nucleus J. P. Fouassier and D. J. Lougnot Kinetic Models for the Development of Density in Radiographic Film. Visible- light Exposure B.W. Darvell Formation of Hydrocarbons from CO + H, using a Cobalt-Manganese Oxide Catalyst. A 13C Isotopic Study M. van der Riet, R. G. Copperthwaite and G. J. Hutchings Surface Reactivity and Spectroscopy of Alkaline-earth-oxide Powders. Part 3.--lH/'H and 180/160 Exchange on Specpure CaO J. Cunningham and C. P. Healy The Thermodynamics of Solvation of Ions. Part 4.-Application of the Tetraphenylarsonium Tetraphenylborate (TATB) Extrathermodynamic As- sumption to the Hydration of Ions and to Properties of Hydrated Ions Y. Marcus A Study of Proton Transfer by 2,2'-Bipyridine from Water to Nitrobenzene using Chronopotentiometry with Cyclic Linear Current-scanning and Cyclic Voltammetry Y. Liu and E. Wang Redox Reactions with Colloidal Metal Oxides.Comparison of Radiation- generated and Chemically-generated RuO2.2H,O and MnO, Colloids A. Harriman, M-C. Richoux, P. A. Christensen, S. Mosseri and P. Neta Non-isothermal Reduction Kinetics and Reducibilities of Nickel and Cobalt Faujasites The Conductivity of Dilute Solutions of Mixed Electrolytes. Part 1 .-The System NaCl-BaC1,-H,O at 298.2 K H. Bianchi, H. R. Corti and R. Fer- nandez-Prini Pairwise Gibbs Function Cosphere-Cosphere Group Interaction Parameters for Alkylammonium Salts in Aqueous Solutions at 298 K; Solubilities of Hydrocarbons in Aqueous Salt Solutions M. J. Blandamer, J. Burgess, M. R. Cottrell and A. W. Hakin C. M. Care G. Schulz-Ekloff, L. Czarnetzki and A. ZukalContents 3055 3061 Heterogeneous Decomposition of Trichlorofluoromethane on Carbonaceous Surfaces Adsorptive Properties of Semiconducting Thin NiO and TiO, Films combined with an Oppositely Polarized Ferroelectric Support Y.Inoue, K. Sat0 and 0. Hayashi Reactions of Alkenes and the Equilibration of Hydrogen and Deuterium on Zirconia R. Bird, C. Kemball and H. F. Leach Calorimetric Investigations of Association in Ternary Systems. Part 4.-The Influence of Solvation on Enthalpy of Complex Formation in Phenol- Tetrahydrofuran and 2,6-Dimethylphenol-Tetrahydrofuran Systems P. G6r- alski and M. Tkaczyk A. J. Colussi and V. T. Amorebieta 3069 3083 89-2Contents 3055 3061 Heterogeneous Decomposition of Trichlorofluoromethane on Carbonaceous Surfaces Adsorptive Properties of Semiconducting Thin NiO and TiO, Films combined with an Oppositely Polarized Ferroelectric Support Y. Inoue, K. Sat0 and 0. Hayashi Reactions of Alkenes and the Equilibration of Hydrogen and Deuterium on Zirconia R. Bird, C. Kemball and H. F. Leach Calorimetric Investigations of Association in Ternary Systems. Part 4.-The Influence of Solvation on Enthalpy of Complex Formation in Phenol- Tetrahydrofuran and 2,6-Dimethylphenol-Tetrahydrofuran Systems P. G6r- alski and M. Tkaczyk A. J. Colussi and V. T. Amorebieta 3069 3083 89-2

ISSN:0300-9599    

DOI:10.1039/F198783FP113

出版商:RSC    

年代:1987

数据来源: RSC

摘要:

JOURNAL OF THE CHEMICAL SOCIETY Faraday Transactions II, lssue9,1987 Molecular and Chemical Physics Dr Nicholas Handy of Cambridge University was invited to contribute a Keynote Paper on the general theme of Potential-energy Surfaces and Reaction Dynamics. He was supported by a group of research workers in the United Kingdom who submitted original papers on cognate subjects. All these papers have now been refereed, and are collected in this month’s issue of Faraday Transactions II. For the benefit of readers of Faraday Transactions I, the contents list is reproduced below. 1577 Accurate Ab Initio Prediction of Molecular Geometries and Spectroscopic Constants, using SCF and MP2 Energy Derivatives N. C. Handy, J. F. Gaw and E. D. Simandiras 1 595 Geometries, Harmonic Frequencies and Infrared and Raman Intensities for H,O, NH, and CH, 1609 An Ab Initio Investigation of N, - - CO+ 1615 Ab Initio Potential-energy Surfaces for the Reactions of Al+ with H, D.M. Hirst 1629 The Diradical Nature of Ketocarbenes occurring in the Wolff Rearrangement. An MC-SCF Study J. J. Novoa, J. J. W. McDouall and M. A. Robb 1637 An Ab Initio Molecular Orbital Study of the Structure and Vibrational Frequencies of CH,MgH 1643 An MCSCF Study of the X 2B2, , A , and 2 ,B, States of Benzyl J. E. Rice, N. C. Handy and P. J. Knowles 1651 The Electronic Structure of CH, and the Cycloaddition Reaction of Methylene with Ethene M. Sironi, M. Raimondi, D. L. Cooper and J. Gerratt 1663 Variational Methods for the Calculation of Rovibrational Energy Levels of Small Molecules 1675 Local Density Approximations and Momentum-space Properties in Light Molecules and Ionic Solids N.L. Allan and D. L. Cooper 1689 Atomic Anisotropy and the Structure of Liquid Chlorine P. M. Rodger, A. J. Stone and D. J. Tildesley 1703 Orientation Dependence of the F+H, Reaction. Analysis of the Angle- dependent Line-of-centres M.odel J. N, L. Connor, 3. C. Whitehead and W. Jakubetz 1719 A Comparison of the Vibrational Predissociation Rates in the Rare- gas-Ethylene Clusters 1733 Trajectory Studies of S+O, and O+S, Collisions W. Craven and J. N. Murrell R. D. Amos J. Baker and A. D. Buckingham G. E. Quelch and I. H. Hillier B. T. Sutcliffe and J. Tennyson A. C. Peet, D. C. Clary and J. M. HutsonCumulative Author Index 1987 Abraham, M. H., 2867 Agnel, J-P. L., 225 Akalay, I., 1137 Akasheh, T., 2525 Akitt, J.W., 1725 Albano, K., 21 13 Alberti, A., 91 Albery, W. J., 2407 Alexandrova, I., 2841 Ali, A.-K. M., 2391 Allen, G. C., 925, 1355 Amorebieta, V. T., 3055 Andersen, A., 2140 Anderson, A. B., 463 Anderson, J, B. F., 913 Antholine, W. E., 151 Ardizzone, S., 11 59 Arias, S., 2619 Arriaga, P., 2705 Atay, N. Z., 2407 Atherton, N. M., 37, 941 Aun Tan, S., 2035 Aveyard, R., 2347 Avnir, D., 1685 Axelsen, V., 107 Bahneman, D. W., 2559 Baker, B. G., 2136 Baldini, G., 1609 Ball, R. C., 2515 Balbn, M., 1029 Barford, W., 2515 Barratt, M. D., 135 Barrer, R. M., 779 Bartok, M., 2359 Basosi, R., 151 Bastein, A. G. T. M., 2103, 2129 Bastl, Z., 51 1 Bateman, J. B., 841 Battesti, C. M., 225 Baussart, H., 1711 Becker, K.A., 535 Beezer, A. E., 2705 Bell, A. T., 2061, 2086, 2087, Bennett, J . E . , 1805, 2421, 2433 Berclaz, T., 401 Berleur, F., 177 Bernal, S., 2279 Berroa de Ponce, H., 1569 Berry, F. J., 615, 2573 Bertagnolli, H., 687 Berthelot, J., 231 Beyer, H. K., 51 1 Bianchi, H., 3027 Bianconi, A., 289 Au, C-T., 2047 2088 Binks, B. P., 2347 Bird, R., 3069 Bjorklund, R. B., 1507 Blandamer, M. J., 559, 865, 1783, 3039 Blyth, G., 751 Boerio-Goates, J., 1553 Bogge, H., 2157 Bond, G. C., 1963, 2071, 2088, 2129, 2130, 2133, 2138, 2140 Borbely, G., 51 1 Botana, F. J., 2279 Boucher, E. A., 1269 Brandreth, B. J., 1835 Brandt, B. A., 2857 Braquet, P., 177 Brazdil, J. F., 463 Breault, R., 21 19 Brede, O., 2365 Brillas, E., 2619, 2813 Briscoe, B. J., 938 Bruce, J. M., 85 Brunton, G., 2421, 2433 Brustolon, M., 69 Brycki, B., 2541 Budil, D.E., 13 Bugyi, L., 2015 Bulow, M., 1843 Burch, R., 913, 2087, 2130, 2134, 2135, 2141, 2250 Burgess, J., 559, 865, 1783, 3039 Burggraaf, A. J., 1485 Burke, L. D., 299 Busca, G., 853, 1591, 2213 Buscall, R., 873 Butt, J. B., 2757 Cairns, J. A,, 913 Care, C. M., 2905 Carley, A. F., 351 Caro, J., 1843, 2301 Carthy, G., 2585 Cassidy, J. F., 231 Celalyan-Berthier, A., 401 Chadwick, D., 2227 Chalker, P. R., 351 Chandra, H., 759 Chengyu, W., 2573 Chieux, P., 687 Chinchen, G. C., 2193 Chittofrati, A., 1159 Choudhery, R. A., 2407 Christensen, P. A., 3001 Christmann, K., 1975 Chu, G., 2533 Chudek, J. A., 2641 Chu, D-Y., 635 Clark, B., 865 Clausen, B. S., 2157 Clifford, A. A., 751 Coates, J. H., 2697, 2751 Colin, A. C., 819 Coller, B.A. W., 645, 657 Coluccia, S., 477 Colussi, A. J., 3055 Compostizo, A., 819 Compton, R. G., 1261 Conway, B. E., 1063 Copperthwaite, R. G., 2963 Corti, H. R., 3027 Corvaja, C., 57 Costa, J. M., 2619 Cottrell, M. R., 3039 Couillard, C., 125 Courbon, H., 697 Craven, J. B., 779 Crossland, W. A., 37 Cummins, P. G., 2773 Cunningham, J., 2973 Czametzki, L., 3015 DAlba, F., 267 Danil de Namor, A. F., 1569, Darvell, B. W., 2953 Dash, A. C., 1307,2505 Dash, N., 2505 Daverio, D., 705 Davies, M. J., 1347 Davoli, I., 289 Dawber, J. G., 771 de Beer, V. H. J., 2145 De Doncker, J., 125 De Laet, M., 125 De Ranter, C. J., 257 Declerck, P. J., 257 Dega-Szafran, Z., 2541 Delafosse, D., 1137 Delahanty, J. N., 135 Delobel, R., 171 1 Despeyroux, B. M., 2081, 2139, 2171, 2243, 2255 Di Lorenzo, S., 267 Diaz Peiia, M., 819 Dimitrijevid, N.M., 1193 Dimov, A. D., 2841 Dodd, N. J. F., 85 Doddridge, B. G., 2697 Domen, K., 2765 Dongbai, L., 2573 Du, J., 2671 Duarte, M. A., 2133 Duce, P. P., 2867 Ducret, F., 141 2663 (ii)AUTHOR INDEX Dudikova, L., 51 1 Dusaucy, A-C., 125 Dutkiewicz, E., 2847 Eicke, H.-F., 1621 Elbing, E., 657, 645 Elders, J. M., 1725 Empis, J. M. A., 43 Endoh, A, 41 1 Engberts, J. B. F. N., 865 Evans, J. C., 43, 135 Fahim, R. B., 1601 Fan, G., 323 Fatome, M., 177 Feakins, D., 2585 Fejes, P., 1109 Fernandez-Prini, R., 3027 Fischer, C-H., 2559 Fletcher, P. D. I., 985, 1493 Flint, N. J., 167 Formaro, L., 11 59 Formosinho, S. J., 431 Forrester, A. R., 211 Forste, C., 2301 Forster, H., 1109 Foster, R., 2641 Fouassier, J.P., 2935 Fox, G. G., 2705 Fraissard, J., 451 Freude, D., 1843 Freund, E., 1417 Fricke, R., 1041 Fujii, K., 675 Fujitsu, H., 1427 Funabiki, T., 2883, 2895 Galli, P., 853 Gampp, H., 1719 Gao, Y., 2671 Garbowski, E., 1469 Garcia, R., 2279 Garrido, J., 1081 Garrido, J. A., 2813 Garrone, E., 1237 Gellings, P. J., 1485 Geoffroy, M., 401 Germanus, A., 2301 Gervasini, A., 705, 2271 Giddings, S., 2317, 2331 Gilbert, B. C., 77 Gilbert, R. G., 1449 Goates, J. R., 1553 Goates, S. R., 1553 Goffredi, M., 1437 Golding, P. D., 1203, 2709, 2719 Goodman, D. W., 1963, 1967, 2071, 2072, 2073, 2075, 2082, 2086, 225 1, 1967 Goralski, P., 3083 Gottschalk, F., 571 Gozzi, D., 289 Grampp, G., 161 Grant, R. B., 2035 Gratzel, M., 1101 Grauer, G. L., 1685 Grauer, Z., 1685 Gray, P., 751 Greci, L., 69 Greenwood, P., 2663 Grieser, F., 591 Grigorian, K.R., 1189 Grimblot, J., 2170 Grossi, L., 77 Groves, G. S., 1281, 1119 Grzybkowski, W., 281, 1253, Gu, T., 2671 Guardado, P., 559 Guilleux, M.-F., 1137 Gunasekara, M. U., 2553 Hada, H., 1559 Hagele, G., 1055 Hakin, A. W., 559, 865, 1783, Halawani, K. H., 1281 Hall, D. G., 967 Hall, D. I., 2693 Hall, M. V. M., 571 Haller, G. L., 2091, 1965, 2072, 2080, 2089, 2091, 2129, 2131, 2132, 2133, 2135, 2136, 2137, 2138,2243 Halpern, A., 219 Hamada, K., 527 Hanke, V.-R., 2847 Harbach, C. A. J., 2035 Harendt, C., 1975 Harland, R. G., 1261 Harrer, W., 161 Harriman, A., 3001 Harris, R. K., 1055 Hartland, G. V., 591 Hasegawa, A., 759, 2803 Hatayama, F., 675 Haul, R., 2083 Hayashi, K., 1795 Hayashi, O., 3061 Hayter, J.B., 2773 Healy, C. P., 2973 Heatley, F., 517, 2593 Hemminga, M. A., 203 Henglein, A., 2559 Henriksson, U., 151 5 Hermann, R., 2365 Herold, B. J., 43 Hertz, H. G., 687 Hidalgo, J., 1029 Higgins, J. S., 939 Hikmat, N. A., 2391 Hilfiker, R., 1621 Hill, W., 2381 Hinderman, J. P., 21 19, 2142, Hindermann, J. P., 21 19 Holden, J. G., 615 Holloway, S., 1935 Hongzhang, D., 2573 Hounslow, A. M., 2459, 2697 Howarth, J. N., 2787, 2795 Howe, A. M., 985, 1007 226 1 3039 2143 Howe, R. F., 813 Hudson, A., 91 Hunger, M., 1843 Hunter, R., 571 Hunter, W. H., 2705 Hussein, F. H., 1631 Hutchings, G. J., 571, 2963 Ichikawa, K., 2925 Ikeyama, N., 1427 Imamura, H., 743 Imanaka, T., 665 Inoue, Y., 3061 Ishikawa, T., 2605 Ismail, H. M., 1601, 2835 Isozumi,Y., 2895 Ito, T., 451 Iwaki, T., 943, 957 Iwamoto, E., 1641 Jackson, S.D., 1835,905 Jaenicke, W., 161, 2727 Janata, E., 2559 Janes, R., 383 JenE, F., 2857 Jones, P., 2735 Joyal, C. L. M., 2757 Joyner, R. W., 1945, 1965, 2074, 2085, 2138, 2249 Juszczyk, W., 1293 Kakuta, 2635 Kakuta, N., 1227 Kameda, Y., 2925 Kaneko, M., 1539 Kanno, T., 721 Kapturkiewicz, A., 2727 Karger, J., 1843, 2301 Kariv-Miller, E., 1169 Karpinski, Z., 1293 Katime, I., 2289 Katuka, N., 2035 Kato, C., 1851 Kawaguchi, T., 1579 Kazansky, V. B., 2381 Kazusaka, A., 1227, 2635 Kemball, C., 3069 Kerr, C W., 85 Kiennemann, A., 21 19 King, D. A., 1966, 2001, 2079, 2080, 2081 Kinoshita, N., 2765 Kira, A., 1539 Kiricsi, I., 1109 Kitagawa, H., 2913 Kitaguchi, K., 1395 Kiwi, J., 1101 Klein, J., 1703 Klinszporn, L., 2261 Klofutar, C., 231 1 Knoche, W., 2847 Knozinger, H., 2088, 2171 Kobayashi, J., 1395 Kobayashi, M., 721 Koda, S., 527 Kondo, Y., 1089 Konishi, Y., 721 (iii)AUTHOR INDEX Koopmans, H.J. A., 1485 Kordulis, C., 627 Korf, S. J., 1485 Korth, H-G., 95 Koutsoukos, P. G., 1477 Kowalak, S., 535 Knstyan, S., 2825 Kubelkova, L., 51 1 Kubokawa, Y., 675, 1761 Kumamaru, T., 1641 Kuroda, K., 1851 Kusabayashi, S., 1089 Kuzuya, M., 1579 La Ginestra, A., 853 Lackey, D., 2001 tajtar, L., 1405 Lambelet, P., 141 Lambert, R. M., 1963, 1964, 2035, 2082, 2083, 2084 Lamotte, J., 1417 Lang, N. D., 1935 Laschi, F., 1731 Laurin, M., 21 19 Lavagnino, S., 477 Lavalley, J-C., 1417 Lawin, P. B., 1169 Lawrence, C., 2331 Lawrence, S., 1347 Le Bras, M., 1711 Leach, H. F., 3069 Leaist, D. G., 829 Lecomte, C., 177 Lee, E.F. T., 1531 Lengeler, B., 2157 Lercher, J. A., 2080, 2255 Leroy, J-M., 1711 Letellier, P., 1725 Levin, M. E., 2061 Lima, M. C. P., 2705 Lin, C. P., 13 Lin, Y-J., 2091 Linares-Solano, A., 1081 Lincoln, S. F., 2459, 2697, Lindgren, M., 893, 1815 Lippens, B. C., Jr, 1485 Liu, R-L., 635 Liu, T., 1063 Liu, Y., 2993 Liwu, L., 2573 Loliger, J., 141 Lorenzelli, V., 853, 1591 Loretto, M. H., 615 Lougnot, D. J., 2935 Luckham, P. F., 1703 Lund, A., 893, 1815, 1869 Luo, H., 2103 Lycourghiotis, A., 627, 1 179 Lynch, J., 1417 Lyons, C. J., 645 Lyons, M. E. G., 299 McAleer, J. F., 1323 McCarthy, S. J., 657 McDonald, J. A., 1007 275 1 Machin, W. D., 1203, 2709, Makkowiak, M., 2541 MacLaren, J. M., 1945, 1965 McLauchlan, K. A., 29 Maestre, A., 1029 Maezawa, A,, 665 Makela, R., 51 Manfredi, M., 1609 Maniero, A.L., 57, 69 Manzatti, W., 2213 Marchese, L., 477 Marcus, Y., 339, 2985 Mari, C. M., 705 Markarian, S. A., 1189 Martin Luengo, M. A., 1347, Martin-Martinez, J. M., 1081 Mashkovsky, A. A., 1879 Masiakowski, J. T., 893, 1869 Masliyah, J. H., 547 Matralis, H., 1179 Matsuura, H., 789 Maxwell, I. A., 1449 Mead, J., 2347 Mehandru, S. P., 463 Mehnert, R., 2365 Mehta, G., 2467 Meriadeau, P., 2140 Meriaudeau, P., 2 1 13 Merwin, L. H., 1055 Micic, 0. I., 1127 Mijin, A., 2605 Mills, A., 2317, 2331, 2647 Mintchev, L., 2213 Miyahara, K., 1227 Miyata, H., 675, 1761, 1851 Mochida, I., 1427 Molina-Sabio, M., 1081 Monk, C. B., 425 Montagne, X., 1417 Morazzoni, F., 705, 2271 Morimoto, T., 943, 957 Morris, J. J., 2867 Moseley, P. T., 1323 Mosseri, S., 3001 Moyes, R.B., 905 Mozzanega, M-N., 697 Muller, A., 2157 Muiioz, M. A., 1029 Nabiullin, A. A., 1879 Naccache, C., 2 1 13 Nagao, M., 1739 Nagaoka, T., 1823 Nair, V., 487 Naito, S., 2475 Nakai, S., 1579 Nakajima, T., 1315 Nakata, M., 2449 Napper, D. H., 1449 Narayanan, S., 733 Narducci, D., 705 Nayak, R. C., 1307 Nazer, A. F. M., 11 19 2719 1651 Nebuka, K., 2605 Nedeljkovic, J. M., 1127 Nenadovic, M. T., 1127 Neta, P., 3001 Niccolai, N., 1731 Niemann, W., 2157 Nishida, S., 1795 Nogaj, B., 2541 Nomura, H., 527 Nomura, M., 1227, 1779, 2635 Norris, J. 0. W., 1323 Norris, J. R., 13 Norskov, J. K., 1935 Notheisz, F., 2359 Nukui, K., 743 Nuttall, S., 559 O’Brien, A. B., 371 Ochoa, J. R., 2289 Odinokov, S. E., 1879 Ogura, K., 1823 Ohno, M., 1559 Ohno, T., 675 Ohshima, K., 789 Okabayashi, H., 789 Okamoto, Y., 665 Okubo, T., 2487, 2497 Okuda, T., 1579 Okuhara, T., 1213 O’Malley, P.J. R., 2227 Onishi, T., 2765 Ono, T., 675, 1761 Ono, Y., 2913 Otsuka, K., 1315 Ott, J. B., 1553 Page, F., 2641 Paljk, s., 231 1 Pallas, N. R., 585 Parry, D. J., 77 Patel, I., 23 17, 233 1 Patil, K., 2467 Patrono, P., 853 Peden, C. H. F., 1967 Pedersen, E., 2 157 Pedersen, J. A., 107 Pedulli, G. F., 91 Penar, J., 1405 Pendry, J. B., 1945 Penfold, J., 2773 Perez-Tejeda, P., 1029 Pethica, B. A., 585 Pethrick, R. A., 938 Pfeifer, H., 2301 Pichat, P., 697 Pielaszek, J., 1293 Pilarczyk, M., 281, 2261 Pilz, W., 2301 Pizzini, S., 705 Pletcher, D., 2787, 2795 Poels, E. K., 2140 Pogni, R., 151 Pomonis, P. J., 627, 1363 Ponec, V., 1964, 1965, 2071, 2072, 2074, 2083, 2103, 2136, 2138, 2139, 2244, 2251AUTHOR INDEX Primet, M., 1469 Prins, R., 2087, 2136, 2137, 2145, 2169, 2170, 2172 Priolisi O., 57 Pritchard, J., 1963, 2085, 2249 Prugnola, A., 1731 Puchalska, D., 1253 Purushotham, V., 21 1 Radulovic, S., 559 Raffi, J.J., 225 Rajaram, R. R., 2130 Ramaraj, R., 1539 Ramirez, F., 2279 Ramis, G., 1591 Rees, L. V. C., 1531, 1843 Renyuan, T., 2573 Resasco, D. E., 2091 Reyes, P. N., 1347 Richards, D. G., 2138 Richoux, M-C., 3001 Richter-Mendau, J., 1843 Riley, B. W., 2140, 2253 Ritschl, F., 1041 Riva, A., 2213 Riviere, J. C., 351 Roberts, M. W., 351, 2047, 2084, 2085, 2086, 2248 Robinson, B. H., 985, 1007, 2407 Rodriguez-Izquierdo, J. M., 2279 Rodriguez, R. M., 2813 Rodriguez-Reinoso, F., 108 1 Rollins, K., 1347 Roman, V., 177 Romlo, M.J., 43 Rooney, J. J., 2077, 2080, 2086, Rosseinsky, D. R., 231, 245 Rossi, C., 173 1 Rowlands, C. C., 43, 135 Rubio, R. G., 819 Rudham, R., 1631 Sabbadini, M. G. C., 2271 Sakai, K., 2895 Sakai, T., 743, 1823 Sakakini, B., 1975 Sakata, Y., 2765 Sakurai, M., 2449 Salazar, F. F., 2663 Saleh, J. M., 2391 Salmeron, M., 2061 Salmon, T. M. F., 2421, 2433 Sanchez, M., 1029 Sanfilippo, D., 2213 Sangster, D. F., 657 Saraby-Reintjes, A., 271 Sato, K., 3061 Sato, T., 1559 Saucy, F., 141 Savoy, M-C., 141 Sayed, M. B., 1149, 1751, 1771 Scholten, J. J. F., 1966, 2073, 2089 2246, 2255, 2257 Schuller, B., 2103 Schulz-Ekloff, G., 3015 Seebode, J., 1109 Segal, M. G., 371 Segre, U., 69 Self, V. A., 2693 Sendoda, Y., 2913 Sermon, P. A., 1369, 1651, 1667, 2175, 2243, 2256, 2693, 1347 Seyedmonir, S., 813 Shelimov, B.N., 2381 Sheppard, N., 1966, 2075 Sidahmed, I. M., 439 Simonian, L. K., 1189 Smith, B. V., 2705 Smith, D. H., 1381 Smith, G. V., 2359 Smith, J. R. L., 2421, 2433 Soderman, O., 1515 Sokolowski, S., 1405 Solymosi, F., 2015, 2074, 2078, 2081, 2082, 2086, 2137, 2142, 2247 Somorjai, G. A., 2061 Spencer, M. S., 2193, 2245, Staples, E., 2773 Steenken, S., 113 Stevens, D. G., 29 Stevenson, S., 2175 Stone, F. S., 1237, 2080, 2084, Strumulo, D., 2271 Stuckey, M., 2525 Su, Z., 2573 Suda, Y., 1739 Suematsu, H., 2605 Sugahara, Y., 1851 Suppan, P., 495 Sustmann, R., 95 Suzuki, T., 1213 SvetliEid, V., 1169 Swartz, H. M., 191 Swift, A. J., 1975 Symons, M. C. R., 1, 383, 759, Szafran, M., 2541 Szostak, R., 487 Tabner, B. J., 167 Taga, K., 789 Takahashi, N., 2605 Takaishi, T., 41 1, 2681 Tan, W.K., 645 Tanaka, H., 1395 Tanaka, K., 1213, 1779, 1859 Tanaka, K-i., 1859 Tanimoto, M., 2475 Tannakone, K., 2553 Taylor, P. J., 2867 Tempere, J.-F., 1137 Tempest, P. A., 925 Theocharis, C. R., 1601, 2835 ThiCry, C. L., 225 Thomas, T. L., 487 2246, 2247, 2248, 2249, 2250 2254 2803 Thomson, S. J., 1893, 1964, 1965, 2083 Thurai, M., 841 Tiddy, G. J. T., 2735 Tilquin, B., 125 Timmons, R. B., 2825 Tkaczyk, M., 3083 Tomellini, M., 289 Tonge, J. S., 231, 245 Toprakcioglu, C., 1703 Topsxe, H., 2157 Topsare, H., 2157, 2169, 2171 Topsare, N-Y., 2157 Torregrosa, R., 1081 Toyoshima, I., 1213 Trabalzini, L., 151 Trifiro, F., 2213, 2246, 2251, Tsuchiya, S., 743 Tsuiki, H., 1395 Tsukamoto, K., 789 Turner, J.C. R., 937 Tyler, J. W., 925, 1355 Ueno, A., 1395 Ukisu, Y., 1227, 2635 Uma, K., 733 Unwin, P. R., 1261 Vaccari, A., 2213 Vachon, A., 177 van de Ven, T. G. M., 547 van den Boogert, J., 2103 van der Lee, G., 2103 van der Riet, M., 2963 van Santen, R. A., 1915, 1963, Varani, G., 1609 Vattis, D., 1179 Vickerman, J. C., 1975, 2075 Villani, R. P., 2751 Vincent, P. B., 225 Vink, H., 801, 941 Vissers, J. P. R., 2145 Vong, M. S. W., 1369, 1667 Vordonis, L., 627 Vuolle, M., 51 Vvedensky, D. D., 1945 Waddicor, J. I., 751 Waddington, D. J., 2421, 2433 Waghorne, W. E., 2585 Waller, A. M., 1261 Wang, E., 2993 Waters, D. N., 1601 Waugh, K. C., 2193 Wells, C. F., 439, 939, 11 19, Wells, P. B., 905 Whalley, E., 2901 Whan, D. A., 2193 White, A., 2459 White, L. R., 591, 873 Whyman, R., 905 Wickramanayake, S., 2553 Williams, D.E., 1323 Williams, G., 2647 2254 1964, 2077, 2140, 2250 1281Williams, J. O., 323 Williams, R. J. P., 1885 Williams, W. J., 371 Wilson, H. R., 1885 Wilson, I. R., 645, 657 Winstanley, D., 1835 Wojcik, D., 1253 Wurie, A. T., 1651 Wyatt, J. L., 2803 Wyn-Jones, E., 2525, 2735 AUTHOR INDEX Xyla, A. G., 1477 Yamada, K., 743 Yamamoto, Y., 1641, 1795 Yamasaki, S., 1641 Yamashita, H., 2883, 2895 Yanagihara, Y., 1579 Yanai, Y., 1641 Yangbo, F., 2533 Yariv, S., 1685 Yonezawa, Y.. 1559 Yoshida, S., 2883, 2895 Yoshikawa, M., 2883 Yoshino, T., 1823 Yun, D. L., 2251 Zaki, M. I., 1601, 2835 Zhang, Q., 635 Zikanova, A., 2301 Zsigmond, A. G., 2359 Zukal, A., 3015 6/ 1598 6/ 1738 6/ 1998 6/23 14 6/23 19 6/2330 612340 612368 612499 6/2500 71204 71205 71206 7/30 1 The following papers were accepted for publication in Faraday Transactions I during June 1987 Interaction of Water with Non-electrolytes.The System Water - Acetonitrile - 1,4-Dioxan Effect of the Surface Structure of Metal Oxides on their Adsorption Properties K. Hadjiivanov, D. Klissurski and A. Davydov A Polarimetric Study of the Interaction of the Tetrahydroxyborate Ion with Carbohydrates J. C. Dawber, J. G. Dawber and S. Gabrail Thermal Decomposition of Silver Squarate A. K. Galwey, M. A. Mohamed and M. E. Brown L-edge EXAFS Studies of the Coordination of Lead in PbO-PbF, Glasses B. G. Rao, K. J. Rao and J. Wong An Extended X-Ray Absorption Fine Structure Study of Heat-treated Cobalt-Porphyrin Catalysts supported on Active Carbon B.van Wingerden, J. A. R. van Veen and C. J. T. Mensch Solvent Effects on the Reactions of Complex Ions. Part 2.-Kinetics of Aquation of cis-( Benzimidazole) (Chloro)bis(ethylenediamine) A. C. Dash and N. Dash Adsorption of Carbon Dioxide, Ammonia and Pyridine on Sodium-modified Silicalite Mechanism of Electrohydrodimerization of 2-Cyclohexen- 1 -one on Mercury from Aqueous Solutions M. Y. Duarte, C. Malanga, L. Nucci, M. L. Foresti and R. Guidelli Mechanism of Electrohydrodimerization of 2-Cyclohexen- 1 -one on Mercury form Aqueous Solution containing Triton X-100 M. Y. Duarte, G. Pezzatini and R. Guidelli The Behaviour of Uranium Metal in Hydrogen Atmospheres G. C. Allen and J. C. H. Stevenes The Thermodynamics of Solvation of Ions. Part 3.-The Heat Capacity for Solvation of Gaseous Ions in Methanol at 298.15 K M.H. Abraham, Y. Marcus and K. G. Lawrence. Molecular Motions in (CH)CCl by 'H-N.M .R. Spin-Lattice Relaxation T. Hasebe and S. Ohtani A Photoconductivity Study of Electron Transfer between CdS and TiO, Powders in Vacuum or in an 0, Atmosphere P. Pichart, E. Borgarello, J. Disdier, J-M. Herrmann, E. Palizzetti and N. Serpone P. Mirti and V. Zelano Y. Matsumura, K. Hashimoto and S. Yoshida (vi)71337 Solutions of Organic Solutes. Part 2.-Moderately Polar Compounds in Water. Limiting Volumes and Compressibilities J. V. Leyendekkers 71346 71 3 58 71417 71465 71470 71483 71484 71497 71528 71529 71532 71545 71 546 71555 7/569 71581 Kinetic and Equilibrium Studies at the Solid Liquid Interface. The Adsorption of Sodium Hexadecyl Sulphate on Polystyrene Latex D.Painter, D. G. Hall and E. Wyn-Jones Paramagnetic Rhodium Species in Zeolites : Part 2.-RhNa-X A. Sayari, J. R. Morton and K. F. Preston 2D ENDOR Imaging based on Differences in Oxygen Concentration E. G. Janzen, Y. Kotake and U. M. Oehler Carbon Monoxide Adsorption on Silica-supported Iron Catalysts C. Johnston, N. Jorgensen and C. Rochester Tin Dioxide Gas Sensors. Part 2.-The Role of Surface Additives J. F. McAleer, P. T. Moseley, J. 0. W. Norris, D. E. Williams and B. C. Tofield Electrochemical Studies of Hydrogen in Ordered and Disordered PdMn Alloys Adsorption and Decomposition of Ammonia on Fe ( I x I ) Overlayer on Ru(OO1) Surfaces with or without Coadsorbed Oxygen C. Egawa, K. Sawabe and Y. Iwasawa The Kinetics of the Oxidation of Hydrogen Peroxide by Bis(2,2'-bipyridine)- manganese(Ir1) Ions in Aqueous Perchlorate Media M.P. Heyward and C. F. Wells Reaction of the Aquacopper(1) Ion with Hydrogen Peroxide. Evidence for a Cu'" (Cupryl) Intermediate G. R. A. Johnson, N. B. Nazhat and R. A. Saadalla-Nazhat Infrared Studies of Adsorbed Species of H,, CO and CO, over ZrO, J. Kondo, H. Abe, Y. Sakata, K. Maruya, K. Domen and T. Onishi Thermal Stabilities of Molybdenum Hexacarbonyl and Subcarbonyls Encapsulated in NaY and NaX Zeolites Y. Okamoto, A. Maezawa, H. Kane, I. Mitsushims and T. Imanaka The Dehydration of Na,S,O, - 5H,O Single Crystals as studied by Thermal Analysis and Optical Microscopy Investigation of the Coordination of Lead in PbO-PbF, Glasses using XANES Complexation of Polymer-bound Iminodiacetate-type Chelating Agent with some Transition-metal Ions. Effect of Charged Polymer Chain on the Chelate Formation Reactions Heat Capacities and Volumes of Mixtures of N,N-Dimethylformamide with Isobutanol, s-Butanol and t-Pentanol.An Analysis of the Water-Non-electro- lyte Enthalpic Pair Interaction Coefficients in N,N-Dimethylformamide Solution Thermodynamics of Fluorocarbon-Hydrocarbon Mixtures. The Systems formed by 2,2,4-Trimethylpentane with Hexafluorobenzene and with Hexafluorobenzene-Benzene J. Aracil, R. G. Rubio, M. Caceres, M. D. Pena and J. A. R. Renuncio K. Baba, Y. Sakamoto and T. B. Flanagen G. G. T. Guarini and S. Piccini K. J. Rao, B. G. Rao and J. Wong Y. Kurimura and K. Takato H. Piekarski and G.Somsen (vii)71585 71608 71630 7/63 1 71632 71635 71680 71740 7/742 7/779 71798 7/845 71902 71942 71973 71993 711030 7/ 1039 Solvent Properties of Polyaromatic Hydrocarbons G. Geblewicz and D. J. Schiffrin An ab initio Molecular-orbital Study of the Structure and Spectroscopic Properties of CH,AlH G. E. Quelch and I. H. Hillier The Phase Response of the Explodator M. Eszterie, Z. Noszticzius and Z. A. Schelly Analysis of Temperature-programmed Diffusion Chromatograms obtained with Zeolite (Gas) Systems The Behaviour of Encapsulated Non-polar Gases in Cs, Na-A Zeolite D. Fraenkel, B Ittah and M. Levy Structure and Reactivity of Zn-Cr Mixed Oxides. Part 1.-The Role of Non- stoichiometry on Bulk and Surface Properties M. Bertoldi, G. Busca, B. Fubini, E.Giamello, F. Triffiro and A. Vaccari Excess Enthalpies and Excess Volume of [o.502 + 0.5C2H,] in the Supercritical Region Enthalpic Pair Interaction Coefficients of NaI-Non-electrolyte in DMF Solu- tion at 25 "C. A Comparison of Electrolyte-non-electrolyte Interactions in DMF and in Aqueous Solutions H. Piekarski A 'H N.M.R. Chemical-shift Study of Inverted Microemulsions of Aerosol OT in Benzene and Cyclohexane. Partitioning of Water between Hydrocarbon and Aqueous Phases Ionisation Constants of 'OH and HO; in Aqueous Solution up to 200 "C. A Pulse-radiolysis Study G. V. Buxton, N. D. Wood and (in part) S. Dyster Radical Cations of Nitroso Derivatives. A Radiation-chemical and Electron Spin Resonance Study H. Chandra, D. J. Keeble and M. C. R. Symons The Effect of the LOMI Reagent Tris(picolinato)vanadium( 11) Formate on the Surface Morphology and Composition of Crystalline Iron Oxides G.C. Allen, C. Kirby and R. M. Sellers Spectrochemistry of Solutions. Part 20.l-The Infrared, Near-infrared and Visible Spectra of Liquid Ammonia The E.P.R. Powder Spectrum of ReIV in TiO,. E. J. Reijerse, P. Stam, C. P. Keijzers, M. Valigi and D. Cordischi Biomolecular Dynamics and Electron Spin Resonance Spectra of Copper Complexes of Antitumor Agents in Solution. Part 2.-Rifamycins R. Basosi, R. Pogni, E. Tiezzi, W. E. Antholine and L. C. Moscinsky N, and (CN), Spin-Lattice Relaxation in KCN Crystals H. J. Kalinowski, and L. C. Scavarda do Carmo Hydrogen Bonding. Part 3.-Enthalpies of Transfer from 1,1,1,- Trichloroethane to Tetrachloromethane of Phenols, N-Methylpyrrolidinone (NMP) and Phenol-NMP Complexes M.H. Abraham, P. P. Duce, D. V. Prior, R. A. Schulz, J. J. Morris and P. J. Taylor Single-crystal E.S.R. Studies on Radiation-produced Species in Ice I,. Part 2.-HO, Radicals J. Bednarek and A. Plonka D. Fraenkel and A. Levy C. J. Wormald and J. M. Eyears F. Heatley J. C. Dougal, P. Gans and J. B. Gill (viii)THE FARADAY DIVISION OF THE ROYAL SOCIETY OF CHEMISTRY GENERAL DISCUSSION No. 85 Solvation University of Durham, 28-30 March 1988 Organ ising Committee : Professor M. C. R. Symons (Chairman) Professor J. S. Rowlinson Professor A. K. Covington Dr I. R. McDonald The purpose of the Discussion is to compare solvation of ionic and non-ionic species in the gas phase and in matrices with corresponding solvation in the bulk liquid phase.The aim will be to confront theory with experiment and to consider the application of these concepts to relaxation and solvolytic processes. Contributions for consideration by the organising Committee are invited in the following areas: (a) Gas phase non-ionic clusters (b) Liquid phase non-ionic clusters (c) Gas phase ionic clusters (d) Liquid phase ionic solutions (e) Dynamic processes including solvolysis The preliminary programme may be obtained from: Mr. Y. A. Fish, The Royal Society of Chemistry, Burlington House, London W1V OBM. Dr J. Yarwood DrA. D. Pethybridge Professor W. A. P. Luck Dr D. A. Young THE FARADAY DIVISION OF THE ROYAL SOCIETY OF CHEMISTRY GENERAL DISCUSSION No. 86 Spectroscopy at Low Temperatures University of Exeter, 13-15 September 1988 Organising Committee: Professor A.C. Legon (Chairman) Dr P. B. Davies Dr 8. J. Howard Dr P. R. R. Langridge-Smith Dr R. N. Perutz Dr M. Poliakoff The Discussion will focus on recent developments in spectroscopy of transient species (ions, radicals, clusters and complexes) in matrices or free jet expansions. The aim of the meeting is to bring together scientists interested in similar problems but viewed from the perspective of different environments. Contributions for consideration by the Organising Committee are invited. Titles should be submitted as soon as possible and abstractsof about300words by30 September 1987 to: Professor A. C. Legon, Department of Chemistry, University of Exeter, Exeter EX4 4QD. Full papers for publication in the Discussion volume will be required by May 1988.THE FARADAY DIVISION OFTHE ROYAL SOCIETY OF CHEMISTRY WITH THE ASSOClAZlONE ITALIANA DI CHIMICA FISICA, DIVISION DE CHlMlE PHYSIQUE OF THE SOCIETC FRANCAISE DE CHlMlE AND DEUTSCHE BUNSEN GESELLSCHAFT FUR PHYSIKALISCHE CHEMIE JOINT MEETING Structure and Reactivity of Surfaces Centro Congressi, Trieste, Italy, 13-16 September 1988 Organising Committee: M.Che V. Ponec F. S. Stone G. Ertl R. Rosei A. Zecchina The conference will cover surface reactivity and characterization by physical methods: (i) Metals (both in single crystal and dispersed form) (ii) Insulators and semiconductors (oxides, sulphides, halides, both in single crystal and dispersed forms) (iii) Mixed systems (with special emphasis on metal-support interaction) The meeting aims to stimulate the comparison between the surface properties of dispersed and supported solids and the properties of single crystals, as well as the comparison and the joint use of chemical and physical methods.Further information may be obtained from: Professor C. Morterra, lnstituto di Chimica Fisica, Corso Massimo D'Azeglio 48, 10125 Torino, Italy. THE FARADAY DIVISION OF THE ROYAL SOCIETY OF CHEMISTRY SYMPOSIUM Orientation and Polarization Effects in Reactive Collisions To be held at the Physikzentrum, Bad Honnef, West Germany, 12-14 December 1988 Organising Committee: Dr S. Stoke Professor R. N. Dixon Professor J. P. Simons Dr K. Burnett Professor H. Loesch Professor R. A. Levine The Symposium will focus on the study of vector properties in reaction dynamics and photodissociation rather than the more traditional scalar quantities such as energy disposal, integral cross-sections and branching ratios.Experimental and theoretical advances have now reached the stage where studies of Dynamical Stereochemistry can begin to map the anisotropy of chemical interactions. The Symposium will provide an impetus to the development of 3-D theories of reaction dynamics and assess the quality and scope of the experiments that are providing this impetus. Contributions for consideration by the Organising Committee are invited in the following areas: (A) Collisions of oriented or rotationally aligned molecular reagents (B) Collisions of orbitally aligned atomic reagents (C) Photoinitiated 'collisions' in van der Waals complexes (D) Polarisation of the products of full and half-collisional processes Abstracts of about 300 words should be sent by 31 October 1987 to: Professor J.P. Simons, Department of Chemistry, University of Nottingham, University Park, Nottingham NG7 ZRD Full papers for publication in the Symposium volume will be required by 15 August 1988.FARADAY DIVISION INFORMAL AND GROUP MEETINGS Industrial Physical Chemistry Group The Interaction of Biologically Active Molecules and Membranes To be held at Girton College, Cambridge on 8-10 September 1987 Further information from Dr T. G. Ryan, ICI New Science Group, PO Box 11, The Heath, Runcorn WA7 4QE Polymer Ph ysics Group Biennial Meeting To be held at University of Reading on 9-1 1 September 1987 Further information from Dr D.Bassett, Department of Physics, University of Reading, Reading RG7 2AD Neutron Scattering Group Applications of Neutron and X-Ray Optics To be held at the University of Oxford on 14-15 September 1987 Further information from Dr R. K. Thomas, Physical Chemistry Laboratory, South Parks Road, Oxford OX1 3QZ Surface Reactivity and Catalysis Group New Methods of Catalyst Preparation and Characterization To be held at Brunel University on 14-16 September 1987 Further information from: Dr M. Bowker, ICI New Science Group, PO Box 11, The Heath, Runcorn, Cheshire WA7 4QE Colloid and Interface Science Group Polydispersity in Colloid Science To be held at the University of Nottingham on 15-16 September 1987 Further information from Dr.R. Buscall, ICI plc, Corporate Colloid Science Group, PO Box 11, The Heath, Runcorn WA7 4QE Polymer Ph ysics Group New Materials To be held at the University of Warwick on 22-25 September 1987 Further information from Dr M. J. Richardson, Division of Materials Applications, National Physical Laboratory, Queens Road, Teddington, Middlesex TW11 OLW Division A utum n Meeting Spectroscopy of Gas-phase Molecular Ions and Clusters To be held at the University of Nottingham on 22-24 September 1987 Further information from Professor J. P. Simons, Department of Chemistry, University of Nottingham, Nottingham NG7 2RD Polymer Ph ysics Group with the Institute of Marine Engineers Polymers in a Marine Environment To be held in London on 14-16 October 1987 Dr G.J. Lake, MRPRA, Brickendonbury, Herts SG13 8NL ~ ~ Electrochemistry Group with the SCI Electrosynthesis To be held at the University of York on 15-17 December 1987 Further information from Dr G. Kelsall, Department of Mineral Resources Engineering, Imperial College, London SW7 2AZ Neutron Scattering Group Scattering from Disordered Systems To be held at the University of Bristol on 16-18 December 1987 Further information from: Dr R. J. Newport, Physics Laboratory, The University, Canterbury, Kent CT2 7NRElectrochemistry Group Workshop on Electrochemical and Non-electrochemical Surface Spectroscopy To be held a t the University of Southampton on 6-7 January 1988 Further information from: Dr S. P. Tyfield, Research Department, CEGB, Berkeley Nuclear Laboratories, Berkeley, Gloucestershire GL13 9PB Division with Electrochemistry Group: Annual Congress Solid State Materials in Electrochemistry To be held at the University of Kent a t Canterbury on 12-1 5 April 1988 Further information from Mrs Y. A. Fish, The Royal Society of Chemistry, Burlington House, London W1V OBN Electrochemistry Group with the SCI Electrolytic Bubbles To be held at Imperial College, London on 21 May 1988 Further information from: Professor W. J. Albery, Department of Chemistry, Imperial College, London SW7 2AZ Gas Kinetics Group Xth International Symposium on Gas Kinetics To be held at University College, Swansea on 24-29 July 1988 Further information from: Dr G. Hancock, Physical Chemistry Laboratory, South Parks Road, Oxford OX1 3QZ THE FARADAY DIVISION OF THE ROYAL SOC SYMPOSIUM No. 23 Molecular Vibrations University of Reading, 15-16 December 1987 Organising Committee: Professor I. M. Mills (Chairman) Dr M. S. Child ~~~ ETY OF CHEMISTRY Dr J. E. Baggott Professor A. D. Buckingham Dr N. C. Handy Dr B. J. Howard The Symposium will focus on recent advances in our understanding of the vibrations of polyatomic molecules. The topics to be discussed will include force field determinations by both ab initio and experimental methods, anharmonic effects in overtone spectroscopy, local modes and anharmonic resonances, intramolecular vibrational relaxation, and the frontier with molecular dynamics and reaction kinetics. The final programme and application form may be obtained from: Mrs. Y. A. Fish, The Royal Society of Chemistry, Burlington House, London W1V OBN (xii)

ISSN:0300-9599    

DOI:10.1039/F198783BP117

出版商:RSC    

年代:1987

数据来源: RSC

摘要:

J . Chem. SOC., Faraday Trans. I , 1987, 83 (9)’ 2693-2696 A New Pressure-programmed Volumetric Method of Measuring Adsorption at the Gas-Solid Interface D. Ian Hall, Valerie A. Self and Paul A. Sermon* Department of Chemistry, Brunel University, Uxbridge, Middlesex UB8 3PH A new pressure-programmed apparatus for measuring extents of adsorption at the gas-solid interface is described. Results obtained indicate that it estimates the extent of hydrogen chemisorption on silica-supported plati- num at 293 K more precisely than traditional volumetric methods. Methods of overcoming the difficulties of measuring the extents of adsorption at solid-solution interfaces at equilibrium at high adsorbate concentrations or low solid surface areas by depletion methods have been highlighted ;l these include direct radio- tracer approaches.Problems also exist for measurements at the gas-solid interface at high pressure or low solid surface areas.3 In volumetric measurements of the extents of physical adsorption or chemisorption of gaseous adsorbates4 on solids [see fig. l(a)] the increment in the extent of adsorption 6n at constant catalyst temperature T, and temperature T of pressure measurement is given by where N is the number of the dose to the sample, PdN and p e are the dosing and equilibrium pressures in the Nth dose, & is the dosing volume and is the volume above the sample; the subscript i denotes isothermal conditions. In the first dose = [(Pd,-Pe,) &-(Pe,> K)IRT. The maximum relative errors at adsorption point N are [(2Ap A & +2Ap A ySi>/Sn], and so precision is not directly increased by reducing volumes & and Ki, but the molar fraction of the adsorbate which is surface-held at this adsorption point does improve as & and Ki decrease-Thus for maximum precision minimum deadspaces and maxi- mum control of temperatures (i.e. kO.01 K) are recommended.However, in the adsorption isotherm composed of 1, 2, 3, . . . N - 1,N adsorption points the maximum errors are cumulative and equal to [(2Ap A & +2Ap A V,,>/6nI1 + , . . + [(2ApA Vd + 2ApA V,i>/6nIN, which equals This becomes equivalent to the problem of nautical ‘dead reckoning ’, with uncertainties becoming ever larger as the adsorption isotherm progresses. An alternative and potentially attractive mode of volumetric method of measuring the extent of adsorption of a gaseous adsorbate on a solid has been devised; this is now reported.This uses a concept which in principle is the inverse of the vapour-pressure thermometer. The system is shown in fig. 1 (b); alongside the isothermal sample bulb is an adsorbate reservoir R held within a separate temperature controller. The introduction of this reservoir increases the volume above the sample to that shown in fig. 1 (a). This new dead space yS in the presence of the solid adsorbent sample can be deduced by the 26932694 Measuring Adsorption at the Gas-Solid Interface transducer transducer P Fig. l(a) Volumetric apparatus for measurement of the extent of adsorption at the gas-solid interface of solid sample S. pd and p , are pressures measured on a calibrated transducer (to an accuracy f Ap) in 6 before dosing and in (5 + v,> after the dose has been admitted to the sample and allowed to reach equilibrium.The sample bulb is held in a thermostat and hence V, carries the i subscript to indicate the isothermal conditions for this sample volume. (b) New vofumetric adsorption system where the incorporation of the adsorbate reservoir R increases the dead space above the sample to KT, which varies with TR, the temperature of the reservoir. expansion of He in the normal manner after closing tap t,, but the apparent volume V, above the sample and after tap t, will depend upon the temperature TR at which reservoir is held (i.e. is KT). Indeed in the calibration where 5, 6 and are the constituent volumes of KT which are held at the temperature T of pressure measurement (ambient), the adsorbent sample temperature T,, and the reservoir temperature TR, respectively. Therefore Hence a plot of (pd/pe-l) us.l/TR at constant G, T and T, gives 1/3 as the gradient and (V,/T+ KJT,) as the intercept [as shown in fig. 2(a)J. However, more important is the apparent dead space above the adsorbent KT.measured with respect to temperature T. Fig. 2(b) shows the apparent volume KT, which does not depend on P d (since pd cc Pe,), but only upon TR at constant T, T,, 4, & and 1/3. It is thus t k n possibg to determine the apparent volume K, as a function of TR using He calibrant from a plot of the form of fig. 2(b) or if and & are independently known from a plot of the form of fig.2(a). Consider now if the absorbent sample is evacuated, tap t, is closed, and a dose of adsorbate is introduced at known sample and reservoir temperature via tap t,, then with the maximum error of [(2Ap A & +2Ap A V,T)/dn]. If the reservoir temperature is then increased KT decreases and peN rises, but less than expected as a result of an increased extent of adsorption. Thus an infinite number of adsorption points can be deduced at constant sample temperature as the reservoir temperature is raised. The additional advantage is that the maximum errors remained unchanged throughout and the error on the last point is the same as the first.D. I. Hall, V . A . Self and P. A . Sermon mE 140 0 \ h L- 6 120 - 5 2 100 0 3 -2 80 I z 8 a 2 60- ' 4 0 1 a 2695 - - - - I I 1 I I I I Fig.2(a) Plot of (pd/pe - 1) us. l/TR measured in the volumetric adsorption system in fig. 1 (b) using helium calibrant at two different dosing pressures [PdHe = 0.67 kPa (0) and 2.00 kPa (a)] and hence also different equilibrium pressures. (b) Variation of K, in the volumetric adsorption system in fig. 1 (b) with the reservoir temperature TR measured using He calibrant at two different dosing pressures [PdHe is 0.67 kPa (0) and 2.00 kPa (a) and hence also different equilibrium pressures (peHe) after admission to the sample volume V,,]. The apparent sample dead space P& is therefore temperature-dependent but not dependent on the He dosing pressure pdHe (since this is proportional to peHe). The catalyst EUROPT-1 Pt/SiO, was chosen as the test adsorbent because of its extensive characterisation.Hydrogen chemisorption was selected because the reservoir temperature TR could only be varied between 78 and 800 K, and hence it would have a smaller variation in adsorbate pressure (and hence an) as a result of this mode of operation; thus other adsorbates would be even easier to use in this mode, and present results indicate the minimum precision achievable. Hydrogen chemisorption isotherms on EUROPT- 1 Pt/SiO, have been reported5 and are reproduced in fig. 3. At no pressure up to 40 kPa is the extent of adsorption reaching a saturation or monolayer capacity at ambient temperature ; there is thus uncertainty as to the equation providing the best description of these data.5 Also plotted in fig.3 are2696 Fig. 3. Adsorption isotherms of hydrogen on Pt/SiO, [termed Eurocat or sample K in ref. (5)] measured as the extent of adsorption n us. equilibrium hydrogen pressure pH, at room temperature of 294 K [., 0 and are taken from ref. ( 5 ) and were measured by traditional volumetric methods where Ki was in one instance 9.49 cm3 and contained 0.35 g sample. 0 and 0 denote new duplicate pressure-programmed volumetric data measured here for the extent of adsorption at 293 K [using a larger K, (see fig. 2) and 0.23 g sample]. Agreement is reasonable, as is reproducibility . the results of the new pressure-programmed adsorption measurements as two duplicate runs on Eurocat. It is clear that the reproducibility of the new method is very good and that there is excellent agreement with the results from traditional volumetric measurements, both in terms of the isotherm gradient and intercept. Conclusion The pressure-programmed adsorption method is as valid as the traditional volumetric method of measurement of the extent of adsorption at the gas-solid interface.A wide range of adsorbate pressure can be studied if the reservoir temperature can be varied from close to the adsorbate boiling point to, say, 800-900 K. The errors of this new method are not cumulative and so continuous adsorption isotherms could be recorded if the reservoir temperature is programmed to increase at a linear rate (dT/dt) or better still (dpldt). This increased degree of precision should allow better inspection of iso- therms and isobars (during adsorption and desorption) and hence allow better estimates of the extent of adsorption and surface areas and porosities (from hysteresis in physical adsorption). The provision of a studentship for V.A.S. by the S.E.R.C. is gratefully acknowledged. We would like to thank both referees for their helpful remarks. References 1 C. C. Nunn and D. H. Everett, J . Chem. SOC., Faraday Trans. I , 1983, 79, 2953; C. C. Nunn, R. S. 2 E. L. Mark, R. A. Porter and R. N. Chanda, f. Colloid Interface Sci., 1971, 35, 133. 3 K. J. Masters and H. D. Gesser, J . Phys. E, 1981, 14, 1043. 4 S. J. Gregg and K. S. W. Sing, Ahorption, Surface Area and Porosity (Academic Press, New York, 5 A. R. Berzins, M. S . W. Lau Vong, P. A. Sermon and A. T. Wurie, Adsorprion Sci. Technol., 1984, 1, 51 ; A. Frennet and P. B. Wells, Appl. Catal., 1985, 18, 243; J. P. Candy, P. Fouilloux and A. J. Renouprez, f. Chem. SOC. Faraday Trans. 1, 1980, 76, 616. Schecter and W. H. Wade, J. Colloid Interface Sci., 1981, 80, 598. 1982) ; ASTM-D3663-78 ; ASTM-D3908-80. Paper 61619; Received 24th April, 1986

ISSN:0300-9599    

DOI:10.1039/F19878302693

出版商:RSC    

年代:1987

数据来源: RSC

摘要:

J. Chem. SOC., Faraday Trans. I , 1987, 83 (9), 2697-2703 The Inclusion of Diflunisal? by a- and P-Cyclodextrins A 19F Nuclear Magnetic Resonance and Spectrophotometric Study Stephen F. Lincoln,* Andrea M. Hounslow, John H. Coates" and Bruce G. Doddridge Department of Physical and Inorganic Chemistry, University of Adelaide, South Australia 5001, Australia The complexation of the diflunisal anion (DF) by a-cyclodextrin (aCD) and P-cyclodextrin (PCD) in aqueous solution at pH 7.00 at 298.2 K has been studied by 19F n.m.r. and u.v.-visible spectroscopy. The formation of 1 : 1 and 1 : 2 inclusion complexes by PCD proceeds through the two equilibria : K l DF+PCD+DF-PCD characterised by Kl = (1.81 k0.20) x lo5 dm3 mol-' and K, = (3.07k 0.25) x lo3 dm3 mol-'. In the presence of aCD only the DF-aCD complex, characterised by Kl = 17.0k0.9 dm3 mol-', is detected.Cyclodextrins are a- 1,4-1inked cyclic oligomers of D-glucopyranose which form inclusion complexes with a wide range of substrates in aqueous ~olution.l-~ These complexes are of substantial intrinsic interest because only secondary bonding occurs between the substrate and the cyclodextrin, and the nature of the substrate can vary from monatomic anions through metal-complex ions to complex organic dye and drug species.1+3 As a consequence of this, cyclodextrin inclusion complexes have attracted substantial interest as models for enzyme-substrate5 and drug-receptor systems, and have found practical applications which include their use as catalysts and micro-encapsulating agents for pharmacologically important compounds.2, Diflunisal, whose structure is shown below, is an experimental anti-inflammatory drug.1° The presence of the fluorine substituents of diflunisal facilitates the study of its inclusion by cyclodextrins using "F n.m.r. spectroscopy6. ' in conjunction with u.v.- visible spectrophotometric studies of the same phenomenon. Thus we report the characterisation of the equilibria governing the inclusion of the diflunisal anion (DF) by a-cyclodextrin (aCD) and P-cyclodextrin (PCD). diflunisal Experimental The cyclodextrins (Sigma) and diflunisal (Merck, Sharp and Dohme) were stored as the anhydrous materials over P205 in a vacuum desiccator prior to use. Solutions of the cyclodextrins and DF alone or together were made up in a 10% D20/KH2P0,- t Systematic name for diflunisal : 2-hydroxy-5-(2,4-difluorophenyl)benzoic acid. 26972698 Inclusion of Dijlunisal by Cyclodextrins Na2HP0, buffer solution at pH 7.00 and 0.1 mol dm-3 ionic strength.Diflunisal in the acid form (pK, “N 3) is virtually insoluble in water, but its conjugate base is water- soluble. 19F n.m.r. spectra were run on a Bruker CXP 300 n.m.r. spectrometer at 282.35 MHz locked on the D 2 0 deuterium frequency. An average of 5000 transients was collected for each spectrum into an 8192-point data base. The samples in 5 mm n.m.r. tubes were thermostatted at 298.2 K. Chemical shifts were measured relative to a 2% solution of sodium trifluoroacetate in D,O sealed in a capillary. The use of this external reference was necessitated by the known ability of cyclodextrins to include trifluoroacetate.The error introduced into the determination of the chemical shifts resulting from their measurement from this external reference has previously been shown to be negligible.6 U.v.-visible spectra were run in silica cells on a Zeiss DMR 10 double-beam spectrophotometer equipped with a thermostatted (k 0.1 K) cell block. All spectra were run in duplicate, and in the case of the PCD solutions were recorded digitally on to paper tape at 1 nm intervals over the range 230-350 nm, and were analysed using a Cyber 173 computer. Only very small absorbance changes were observed with change in aCD concentration and accordingly no attempt was made to analyse them. Results The resonances of DF observed in a 5.00 x mol dme3 solution in 10 % D 2 0 at pH 7.00 at 298.2 K appear at -36.92 ppm and -39.40 ppm, respectively, from an external reference of 2% sodium trifluoroacetate in D20.The resonance of the 2-F of DF is a multiplet (components at - 39.30, - 39.33, - 39.36 and - 39.39 ppm of relative intensity 7.18, 14.8, 15.3 and 6.87, respectively) which collapses to a doublet (JF+ = 7.22 Hz) under broad-band lH decoupling. The resonance of the 4-F is also a multiplet (components at - 36.82, - 36.85, - 36.87, - 36.90 and - 36.93 ppm of relative intensity 7.13, 15.2, 20.0, 15.5 and 8.50, respectively) which collapses to a doublet = 7.20 Hz) under broad-band ‘H decoupling. Some broadening of the hyperfine structure of these DF resonances was observed in the presence of aCD and PCD, but separate resonances for DF in the free state and its included states were not observed, consistent with exchange between these environments being in the fast-exchange limit of the n.m.r.timescale. The variations of the DF 19F chemical shift with total aCD concentration, which are consistent with the formation of a 1 : 1 inclusion complex as shown in eqn (1) (later), are shown in fig. 1. (The total DF concentration was constant at 4.81 x mol dmP3 and the total aCD concentration varied in the range 0-0.1246 mol dm-3.) Also shown in fig. 1 are the best-fit lines corresponding to a simultaneous non-linear least-squares fit of the 2-F and 4-F data to eqn (2), which corresponds to the form of the chemical-shift variation expected from eqn (l), and in which 6 is the observed chemical shift, 6, is the chemical shift of free DF, and 6, is the chemical shift of DF-aCD.In this fitting procedure 6, was set constant at - 36.89 and - 39.37 ppm for 4-F and 2-F, respectively, and the 6, and Kl values, derived using eqn (1) and (2), appear in table 1 : K , DF + aCD DF *aCD d,[DF] + 6,[DF - aCD] [DF] + [DF *aCD] * s = The change in the u.v.-visible spectrum of DF over the same aCD concentration range as that employed in the 19F n.m.r. study was insufficient for an assessment of the inclusion process. This is in marked contrast to the situation in the presence of PCD, where the inclusion processes produce a progressive decrease in molar absorbanceS. F. Lincoln et al. 2699 -36 t -40 I I I I I I I [aCD]/ 1 0-2 mol dmW3 0 4 8 12 Fig.1. Variation of the 19F chemical shift (6) of DF (4.81 x mol dm-3) with total a- cyclodextrin concentration, [aCD]. (a) 4-F, (6) 2-F. The negative shifts signify upfield shifts from a 2 YO sodium trifluoroacetate solution in D,O external reference which is assigned a shift of zero. The solid curves represent the best fits of these data to eqn (2). Table 1. Equilibrium constants and lgF chemical shifts" for diflunisal anion<yclodextrin systems in 10% D,O aqueous KH,PO,-Na,HPO, buffer solution at 0.1 ionic strength, pH 7.00 and 298.2 K a-cyclodextrin - (4-F) - 36.89 f 0.01 - 38.18 f 0.03 (2-F) -39.37f0.01 -38.27f0.03 0.0 1 70 f 0.0009 - - P-cyclodextrin 181 f20" 3.07 & 0.25" (4-F) - 36.92 f 0.01 - 34.91 f0.05 - 34.52 f 0.05 (2-F) - 39.40 f 0.01 - 36.71 & 0.05 - 36.34 f 0.05 a A negative shift signifies an upfield shift from a 2% sodium trifluoroacetate solution in D,O external reference which is assigned a shift of zero.The 6, values vary slightly with DF concentration and hence different values appear in the table for the aCD and PCD systems. The digital resolution was 0.007 ppm. Determined from u.v.-visible spectrophotometric data. Determined from 19F shift data. (fig. 2). This spectral variation was obtained after correction for light-scattering effects arising from PCD. The light-scattering contribution to the observed absorbance was determined from spectrophotometric measurements of buffered solutions of /3CD alone in the wavelength range 230-350 nm. The spectral variation seen in fig. 2 is consistent with the formation of a 1 : 1 and a 1 : 2 inclusion complex as shown in eqn (3) and K, (4) : DF+PCDeDF-PCD (3) The variation of the molar absorbance in the range 240-255 nm was subjected to a non- linear least-squares analysis using the equation A = EJDF] + E,[DF *pCD] + e,[DF - (PCD),]2700 Inclusion of Dijlunisal by Cyclodextrins 2 1 250 300 350 0 X/nm Fig. 2.The variation of the u.v.-visible spectrum of DF (1.713 x mol dm-3) in the presence of PCD. At 250 nm the molar absorbance decreases systematically as the total PCD concentration increases in the sequence: 0, 6.171 x (1.399, 2.809 and 6.779) x lop4, (1.179 and 3.387) x mol dm-3. These seven spectra illustrate the trend in spectral variation observed for the 19 solutions studied, whose total PCD concentrations were encompassed by the range given above.which describes the variation of the observed molar absorbance ( A ) with concentration resulting from the equilibria of eqn (3) and (4), and in which E,, E, and c2 are the molar absorbances of DF, DF -PCD and DF - (PCD),, respectively. K , and K, given in table 1 were derived via a non-linear least-squares fit of the molar absorbance variation at 1 nm intervals in the range 240-255 nm. The variation of the DF 19F chemical shift (fig. 3) with total PCD concentration (in the range 0-0.01 161 mol dm-3, which is smaller than that employed for aCD as a consequence of the lower solubility of PCD2) is also consistent with the two equilibria shown in eqn (3) and (4), and is given by 6,[DF] + S,[DF .PCD] + 6,[DF - (PCD),] [DF] + [DF -PCD] + [DF - (PCD),] 6 = in which 6 is the observed chemical shift, 6, is the shift of DF, 6, is the shift of DF -PCD, and 6, is the shift of DF (PCD),.However, because the 19F n.m.r. detection level for DF is several orders of magnitude below that of the u.v.-visible spectroscopic method in this case, a substantially higher total DF concentration (5.00 x mol dm-3) was em- ployed. As a consequence of this and the large Kl and K, values, the equilibrium DF and PCD concentrations are always very small compared to the DF -PCD and DF - (DCD), concentrations, with the result that the Kl = (2.17 9.16) x lo5 dm3 mol-l and K, = (5 15 2000) dm3 mol-' determined through a non-linear least-squares fit of the 19F shift data to eqn (6) are subject to large uncertainties.Thus this data fit is a semi-quantitative confirmation of the existence of the two equilibria shown in eqn (3) and (4). However, when K, and K2 are set equal to the values obtained spectrophotometrically (table 1) and the 19F chemical-shift data are again subjected to a non-linear least-squares fit to eqn (6), the best-fit curve is seen to reproduce closely the experimental 19F chemical-shift variation, as is seen from fig. 3. (The a, 6, and 6, values derived using this fitting procedure appear in table 1 .) Thus the u.v.-visible spectrophotometric data and 19F chemical-shift data are shown to be in good agreement.S. F. Lincoln et al. 270 1 - 34 -36 n E a CQ W -38 0 4 8 [pCD]/10-3 mol dm-3 12 Fig. 3. Variation of the 19F chemical shift (6) of DF (5.00 x mol dm-3) with total p- cyclodextrin concentration, [j?CD] : (a) 4-F, (b) 2-F.The negative shifts signify upfield shifts from a 2 % sodium trifluoroacetate solution in D,O external reference which is assigned a shift of zero. The solid curves represent the variation of 6 predicted by eqn (6) using the Kl and K2 values determined from the u.v.-visible spectrophotometric data. Discussion The inclusion of DF is very sensitive to the dimensions of the cyclodextrin. Thus aCD, which is characterised by an internal annular diameter of 5-6 A, forms only the 1 : 1 complex DF-aCD, which is of only moderate stability (tabje 1); whereas PCD, which is characterised by an internal annular diameter of 7-8 A, forms the 1 : 1 and 1 : 2 complexes DF-PCD and DF.(BCD),, both of which are of high stability (table 1).CPK (Corey-Pauling-Koltun) models show that each end of DF fits further into the PCD annulus than into the aCD annulus, and it is reasonable to assume that this is the major source of the higher stabilities of DF-PCD and DF-(PCD),. It is probable that DF enters through the wider end of the cyclodextrin annulus delineated by the secondary hydroxo groups, but it is not possible to determine unequivocally from the present data whether one or two 1 : 1 complexes are formed in which either end of DF enters the annulus first, as shown schematically in fig, 4. Thus Kl may be a composite equilibrium constant for DFsaCD and DF-PCD, although this seems less likely for the former complex, as is discussed below. The formation of DF.(PCD), is characterised by a K2 significantly less than K,, characterising DF *PCD presumably as a consequence of steric interactions between the two cyclodextrins in DF.(PCD),. (In this case both Kl and K2 may be composite equilibrium constants as shown in fig.4.) In view of t5e well established formation of cinnamate.(aCD), for a range of fluorocinnamates6 it is at first sight surprising that DF-(aCD), was not detected in solution. CPK models show that the benzoate end of DF penetrates the aCD annulus to a lesser extent than does the difluoro end, which suggests the most stable DF .aCD complex may be that in which the difluoro end is included. On this basis the evident low stability of the DF-(aCD), complex becomes less surprising. Any conformational and solvational differences between aCD and PCD may also affect the relative stabilities of their inclusion complexes, but such effects are not readily perceived on the basis of the available data.The chemical shifts of the 2-F and 4-F of DF in its complexes may be interpreted in structural terms if upfield and downfield shifts indicate a fluorine in a hydrophobic environment and adjacent to cyclodextrin hydroxo groups, respectively, as "F studies2702 Inclusion of D$unisal by Cyclodextrins [ PCD only) and K2 = Ki + Ki. Fig. 4. A schematic representation of the inclusion of DF in which aCD and PCD are represented as truncated cones. Kl = Kl + suggest? In DF-aCD the 6, values of 2-F and 4-F are, respectively, downfield and upfield from their 6, values in free DF (table 1).This is consistent with the 4-F moving into a hydrophobic environment, whilst the 2-F remains in a hydrophilic environ- ment.' CPK models suggest that, when the difluoro end of DF is included in DF - aCD, the 4-F resides in the hydrophobic part of the aCD annulus while the 2-F interacts partly with solvent water and partly with the ring of secondary hydroxo groups at the annular entrance. In contrast the 6, and 6, values for both 2-F and 4-F in DF-PCD and DF*(BCD), are downfield from their 6, values and the changes in chemical shift are greater than those observed for the aCD system (table l), consistent with both fluorines interacting with BCD hydroxo groups. This may indicate that the larger annular diameter of BCD allows DF to position 4-F adjacent to the primary hydroxo groups at the narrower end of the annulus, and 2-F adjacent to the secondary hydroxo groups at the wider end of the annulus.CPK models show this to be a plausible explanation. The formation of DF.(BCD), induces relatively small 19F shift variations (6,) for 2-F and 4-F, suggesting that the second PCD largely includes the carboxylate end of DF. These assignments and structural interpretations of the 19F chemical shifts supersede those appearing in a preliminary account of this work." We thank Merck, Sharp and Dohme for a gift of diflunisal, and the Australian Research Grants Scheme for partial support of this research. References W. Saenger, in Inclusion Compounds, ed. J. L. Atwood, J. E. D. Davis and D. D. MacNicol (Academic Press, London, 1984), vol. 2, p. 231. J. Szejtli, in ref. (l), vol. 3, p. 331. R. J. Bergeron, in ref. (l), vol. 3, p. 391. 1. Tabushi, in ref. (l), vol. 3, p. 445. R. Breslow, in ref. (l), vol. 3, p. 473. 1. M. Brereton, T. M. Spotswood, S . F. Lincoln and E. H. Williams, J . Chem. SOC., Faraday Trans. I , 1984, 80, 3147.S. F. Lincoln et al. 2703 7 D. L. Pisaniello, S. F. Lincoln and J. H. Coates, J . Chem. Soc., Furuduy Trans. 1, 1985, 81, 1247. 8 R. L. Schiller, S. F. Lincoln and J. H. Coates, J. Chem. Soc., Furuduy Trans. 1, 1986,82,2123 (in this 9 P. E. Hansen, H. D. Dettman and B. D. Sykes, J . Magn. Reson., 1985, 62, 487. reference ’annular radii ’ should read ‘annular diameters ’). 10 K. F. Tempero, V. J. Cirillo and S. L. Steelman, in Difunisal in Clinical Practice, ed. K. Miehlke 11 S. F. Lincoln, A. M. Hounslow, J. H. Coates and B. G. Doddridge, J . Inclusion Phenom., 1987, 5, Paper 611018; Received 23rd May, 1986 (Futura, Mt. Kisco, NY, 1978), p. 23. 49.

ISSN:0300-9599    

DOI:10.1039/F19878302697

出版商:RSC    

年代:1987

数据来源: RSC

摘要:

J. Chem. SOC., Faraday Trans. I , 1987, 83 (9), 2705-2707 Microcalorimetric Measurement of the Enthalpies of Transfer of a Series of ortho- and para-Alkoxyphenols from Water to Octan-1-01 and from Isotonic Solution to Escherichia coli Cells Anthony E. Beezer,* Maria C. P. Lima,? Gary G. Fox, Paloma ArriagaJ William H. Hunter and Brian V. Smiths Department of Chemistry, Royal Holloway and Bedford New College, University of London, Egham Hill, Egham, Surrey TW20 OEX Enthalpies of transfer for ortho- and para-alkoxyphenols from aqueous isotonic solution to non-growing Escherichia coli are reported. The values are compared, for ortho-alkoxyphenols, to A,,, H for transfer from water to octan-1-01. The values for both ortho- and para-homologues show breaks in At,., H (isotonic aqueous solution to cells) values as a function of carbon number in the side chain = 4.The differences in Atrs H values for ortho-, meta- (published previously) and para-alkoxyphenols are compared. In a previous paper' we reported the enthalpies of transfer (AtrsH) of a series of meta- alkoxyphenols from isotonic solution to Escherichia coli cells. These data were compared with the values for transfer of the same solutes from water to octan-1-01, heptane and propylene 'carbonate' (mutually saturated solvent systems). It was shown that the values for transfer to the biological cells were different in magnitude, showed different trends in the values of AtrsH and that none of the bulk solvents adequately mimicked the properties of the biological membrane. Interest in systems such as these was generated by the existence of linear free-energy relationship^^-^ and their use in, for example, drug structure activity relationships (QSAR).Studies on the solution thermodynamics of these same solutes6 have shown that there are significant differences in the behaviour of the ortho- and meta-alkoxyphenols upon solution in water, water-alcohol solutions and in pure alcohols. These differences it was supposed could be accounted for by the existence of internal hydrogen bonding in the ortho-homologues. The Atrs H data for the transfer of the ortho-homologues to octan- 1- 01 and to E. coli cells should reflect this additional structural feature which is absent in the meta-counterparts. Moreover, we have proposed',' that values of AtrsH may be sensitive discriminators of bulk solvents which mimic the properties of biological lipoid matrices.To examine this proposal and to demonstrate the sensitivity of such measurements we now report the determination of Atrs H for the transfer of a series of ortho- and para-alkoxyphenols from isotonic solution to E. coli and, for comparison, the data on transfer of the ortho-homologues from water to octan-1-01 (both mutually saturated). The data on the meta-homologues showed a linear dependence of AtrsH upon carbon number in the sidechain of the phenol; such a relationship is, of course, at the heart of QSAR. The data for the ortho-homologues will indicate if this is possibly a more general finding and, if so, to what extent group additivity data may be established.t Permanent address : Departmento de Quimica, Universidade de Coimbra, Coimbra, Portugal. 1 Permanent address : Instituto de Quimica Fisica ' Rocasolano ', Madrid, Spain. Q Permanent address : Department of Chemistry, King's College (KQC), Campden Hill Road, London W8. 27052706 Enthalpies of Transfer of Alkoxyphenols Table 1. Molar enthalpies of solution (kJ mol-') for solution of ortho-alkoxyphenols in water saturated with octanol, octanol saturated with water, isotonic solution and to E. coli cells suspended in isotonic solution is0 tonic water- octanol- isotonic solution solute octanol water solution + cells o-methoxy 2.12 f0.02 0.67f0.01 2.10f0.05 2.12 20.01 o-e t hoxy 0.95L0.03 1.94k0.02 0.20f0.01 0.16f0.01 o-propoxy 0.90+0.01 1.74k0.01 0.07f0.01 0.04+0.01 o-butoxy 0.55f0.01 0.91 kO.01 0.34f0.02 0.13f0.01 Experimental The ortho- and para-alkoxyphenols were prepared as described previously.The preparation, storage and recovery of inocula together with the operation of the microcalorimeter were as reported earlier.' Results and Discussion Table 1 shows the molar enthalpies measured for solution of the solutes in water, octan- 1-01 (for ortho-alkoxyphenols, both mutually saturated), isotonic solution and for the molar enthalpy change accompanying addition of the solutes to isotonic solution containing a suspension of E. coli. The calculation schemes follow the methods outlined in our earlier publications.'.' This scheme involves the assumption that the rapid endothermic process is the result of solution in the isotonic solution followed by (rapid) transfer of the solute from solution to the biological membrane.The extended exothermic process (of the order of hours compared with a process which occurs so rapidly that the power-time signal decays with the instrumental time constant of ca. 107 s) is taken to be a result of the biological consequences of solute uptake by the organism. In table 2 we therefore show the derived molar enthalpies of transfer of the solutes for the considered solvent systems. For comparison we also show in table 2 the data published earlier' for these solvent systems relating to transfer of the meta- alkoxyphenols. The obvious difference between the data for the three series is that, whereas values for the meta-homologues are regular and increasingly negative, those for the ortho- homologues (0-methoxy, o-ethoxy and o-propoxy) are essentially zero, that for o-butoxy being negative and within experimental error the same as that for transfer of m- methoxyphenol from isotonic solution to cells.As with the meta-compounds it is again apparent that the molar enthalpy of transfer of these o-alkoxy solutes from water to octan- 1-01 is very different and, except for o-methoxyphenol, endothermic. The data for the para-alkoxyphenols show similar Atrs H values for the p-methoxy, p-ethoxy and p- propoxy homologues, all now being exothermic. In contrast to the ortho-series the Atrs H value for p-butoxyphenol is endothermic. These data appear therefore to confirm that octan-1-01 does not behave as does the biological membrane with respect to these solutes. We also suppose that the reason for the difference in behaviour of the three series of solutes upon transfer between the solvents studied necessarily lies in solute- solute and solute-solvent interactions.Furthermore, it is anticipated that the possible existence of internal hydrogen bonding in the compounds will very much influence the thermodynamic parameters of solution for these solutes. We have noted this feature before' with respect to solution in water-alcohol solvent systems. The implication of the essentially zero value for Atrs H for the first three members ofA . E. Beezer et al. 2707 Table 2. Enthalpies of transfer (kJ mol-') for transfer of ortho- and rneta-alkoxyphenols from water saturated with octanol to octanol saturated with water and for ortho-, meta- and para- alkoxyphenols from isotonic aqueous solution to E.coli cells suspended in isotonic aqueous solution is0 tonic water-octanol solution<ell solute system suspension o-methoxy o-ethoxy o-propoxy rn-methoxy rn-ethoxy rn-propoxy rn-pentoxy p-methoxy p-ethoxy P-P'OPOXY p-butoxy o-butoxy rn-butoxy - 1.44 0.99 0.84 0.3 1 - 8.03 - 6.95 - 6.96 - 0.02 - 0.04 - 0.03 -0.21 -0.22 - 1.1 - 2.02 - 4.06 - 5.14 - 0.28 -0.27 - 0.28 0.30 the ortho- series is, in the light of the demonstrated' biological activity of these solutes, that the process of transfer of these drugs from isotonic solution to the biological cell is entropy-driven. The apparent constancy of the AtrsH values for the first three members of both the ortho- and para-series is surprising, the difference in sign reflecting, no doubt, hydrogen bonding and solute-solvent interactions upon transfer from aqueous medium to the lipoid medium of the biological cell. Of course it is difficult to determine the value of the partition coefficient (and hence Atrs G) for transfer of the drug from isotonic solution to the biological cell, hence we cannot evaluate AtrsS.The observation that there appears to be a break in the plots of A,,,H us. carbon number (n) in the alkyl chain at n = 4 for both ortho- and para-alkoxyphenols is in accord with reports in the literature1'+ l1 that solubility and other physical parameters do indeed show a break when plotted against n. References 1 A. E. Beezer, P. L. 0. Volpe, R. J. Miles and W. H. Hunter, J. Chem. Soc., Faraday Trans. 1, 1986,82, 2 A. E. Beezer, P. L. 0. Volpe and W. H. Hunter, J. Chem. SOC., Faraday Trans. 1, 1986, 82, 2863. 3 R. Lumry and S. Rajender, Biopolymers, 1970, 9, 1125. 4 A. Leo, C. Hansch and D. Elkins, Chem. Rev., 1971, 71, 525. 5 E. Tomlinson, Znt. J . Pharm., 1983, 13, 115. 6 A. E. Beezer, P. L. 0. Volpe, C. A. Gooch and W. H. Hunter, J. Pharm. Pharmacol., 1987, in press. 7 A. E. Beezer, M. C. P. Lima, G. G. Fox, W. H. Hunter and B. V. Smith, Thermochim. Acta, 1987, in 8 A. E. Beezer, W. H. Hunter and D. E. Storey, J. Pharm. Pharmacol., 1980, 32, 815. 9 A. E. Beezer, M. C. P. Lima, C. A. Gooch, W. H. Hunter and B. V. Smith, Znf. J. Pharm., 1987, in 2929. press. press. 10 S. H. Yalkowsky, G. L. Flynn and T. G. Slunick, J. Pharm. Sci., 1972, 61, 1249. 11 R. N. Smith, C. Hansch and M. W. Ames, J. Pharm. Sci., 1975, 64, 599. Paper 6/1175; Received 10th June, 1986

ISSN:0300-9599    

DOI:10.1039/F19878302705

出版商:RSC    

年代:1987

数据来源: RSC

摘要:

J. Chem. Soc., Faraday Trans. I, 1987, 83 (9), 2709-2717 The Vapour Pressure of Benzene Part 1 .-An Assessment of Some Vapour-pressure Equations Peter D. Golding" and William D. Machin Chemistry Department, Memorial University of Newfoundland, St. John's, Newfoundland, Canada A1 B 3x7 Two sets of benzene saturated vapour pressures, accepted as reference data, are regressed according to the Wagner, Ambrose, Scott-Osborn and modi- fied Cox and Clarke-Glew vapour-pressure equations. In each of these equations the optimum number of regression parameters necessary to fit these data is four. The two equations which have a thermodynamic basis, the Scott-Osborn and Clarke-Glew equations, give the best fit of both data sets. The Clarke-Glew equation is shown to have superior interpolative and extrapolative properties as a vapour-pressure equation.To establish the bona fides of an apparatus for vapour-pressure measurement, we have extended the reference benzene vapour-pressure data of Ambrose (set 2/ 1968)l and Scott and Osborn2 to the triple point. While the experimental details of this work are reported in part 2 of this ~eries,~ comparison of our data with extrapolated reference data is required. We have selected five modern vapour-pressure equations as extrap- olation functions, two of which are recommended by Ambrose1*4-8 and two by Scott and Osborn.2 The fifth is a form of the Clarke-Glewg equation for reaction equilibria used by de Kruif and coworkers10-18 to represent vapour pressures. The purpose of the present work is to assess critically which of these equations best represents the reference data.Regression Analysis Regressions of the two sets of reference data according to these vapour-pressure equa- tions are carried out using the Wentworth-Deminglg* 2o algorithm for weighted, non- linear regression. This method of analysis of the temperature (7') dependence of vapour pressure (p) requires the input of reasonably accurate estimates of uncertainties (6p, 6T) to generate weighting factors appropriate to each datum. For the data of others, estimation of the magnitude of these uncertainties poses some difficult^.^. 8 p 21-23 In the regressions here, 6Tis input as +2 mK. We have also adopted a conservative procedure for the estimation of 6p, namely that 6p is taken at the 100 % confidence level with respect to the p residuals (Ap), where Ap is the difference between measured (Pobsd) and calculated (Pcalcd) pressures.That is, 6p for each Pobsd is given by 'P/Pobsd = I 'PIPobsd I max (1) where I AP/Pobsd I max is the largest, absolute, fractional deviation in the data set. Since parameter values in these regressions depend to some small extent upon the uncertainty estimates, the magnitudes of Ap are not entirely independent of 6p. Hence, iteration of the regressions with respect to 6p is required to find the input Sp/pobsd which correctly coincides with the output 1 Ap/pobsd I max. Convergence is rapid in this respect, and based on these 6p estimates, tabulated parameter standard errors represent ca. two standard deviations. Ambrose et a1.'*' and Scott and Osborn2 list criteria for the determination of the allowed number of parameters in vapour-pressure equations, i.e.the optimum order of 27092710 Assessment of Vapour-pressure Equations Table 1. Regression parameters for representations of benzene vapour-pressure data by the Wagner equation” data set Ib ~ parameterd Ambrosee this work data set 11“ this work a0 8.496 57 8.548 57 8.68794 f 0.14248 k0.024 39 -a1 6.982 73 7.661 71 9.436 76 - + 1.8 10 94 & 0.253 67 a2 1.332 13 2.494 70 5.504 54 f 3.068 83 f0.392 53 - as 2.628 63 3.531 87 5.791 01 & 2.300 23 f 0.194 88 -a4 3.333 99 2.33468 - + 2.378 93 - u/Paf 2.13 1.81 2.88 8.51433 0.093 00 7.202 3 1 f 1.25 1 28 1.701 24 f2.16780 2.901 25 & 1.755 59 3.038 74 k2.10996 2.54 8.646 82 f 0.013 68 8.991 29 f 0.150 87 4.80443 f 0.238 49 5.422 97 f 0.127 90 5.31 a Eqn (3) with T, = 562.16 K, after Ambrose el al., cf.ref. (I), (4), (9, (29), (30). * Set 2/1968, ref. (1). Ref. (2). Parameter standard errors are preceded by f beneath quantities. Ref. (1) and (4), but these may represent data in ref. (29) not corrected to IPTS-68, c& ref. (31). f Standard error of estimate, u, is the root-mean-square deviation = [ z ( A ~ ) ~ / ( n - r n ) ] Z , where n is the number of data and rn is the number of parameters. the regression analyses. In this regard, we rigorously apply the I; test (null hypothesis, 99% confidence level) to all regression results below. In addition, all regressions are processed in ‘double precision’ (16 digits x lok3’), save in the case of the Cox equation, where a higher precision (15 digits x lok3’) is required.Carrying out the regressions in ‘single precision’ (6 digits x leads to truncation errors which result in either anomalous or diverging parameter values, or variance and covariance matrices which cannot be inverted. These can be symptomatic of non-augmented or ill-conditioned (Hilbert) 25 The Wagner Equation The ‘determination of the optimum form of vapour-pressure equations and the cor- responding coefficients by statistical methods ’ was extensively described26 by Wagner,27 who recommends an equation of the form26-28 21 lnp, = T;l C a , ( l - 7 3 - 3 ) / 2 i- 1 where the reduced pressure p , is p/pc and the reduced temperature is T/T,. Wagner et aZ.26 report that the more relevant terms are those for i = 5, 6, 9, 17 and 21. A r n b r ~ s e ~ ~ ~ has selected the simplest equation (i = 5, 6, 9 and 15) from Wagner’s analysis28 as a standard form to represent the vapour pressures of 22 compounds, including benzene.29 This equation is given by lnp = a,+(a, z+a, 21*5+a3z3+a4z6)/T, (3) where a, = In pc and z = 1 - q.We have regressed the reference benzene vapour-pressure data’. according to eqn (3). Comparisons of our results with those of Ambrose’~~ are reported in table 1 . The coefficients of the five-parameter fits for our results and those of Ambrose are similar, but differ significantly from those of our four-parameter fit. From statistics related to the ‘goodness of fit’, e.g. standard error of estimate, our parameter values give a slightlyP .D. Golding and W. D. Machin 271 1 Table 2. Regression parameters for representations of benzene vapour-pressure data by the Ambrose equationa parameterb Ambrosec b, 2.333 342 b, 9.17602 -b2 9.000 b3 4.577 - lob, 1.06 1 Ob, 1.73 102b, 6.1 a/Pab 6.83 data set Ib this work data set IIb this work 2.33204 & 0.019 22 9.163 49 k0.162 32 10.15590 f 9.628 74 3.75798 Ifr 3.689 82 5.735 36 7.421 85 - - 1.86 2.34687 * 0.002 35 9.288 73 k0.019 15 2.7 19 97 f 0.960 54 6.6 1023 & 0.257 40 - - - 2.47 2.32943 & 0.01 1 87 9.141 06 & 0.1 00 89 11.54531 k6.213 17 3.18062 & 2.509 57 6.990 34 & 5.793 68 - - 2.49 2.343 72 k 0.00 1 48 9.262 58 k 0.01 2 39 4.053 70 k0.63931 6.209 35 f 0.195 95 - - - 4.70 a Eqn (4) with T,,, = 563 K, Tmi, = 285 K. See footnotes, table 1.Ref. (1) and (30). more faithful representation of the data.? Of more importance, however, is the fact that based on the F test, the fifth parameter is null for both data sets, i.e. a four-parameter fit for these data is statistically preferable to both higher and lower orders of eqn (3). The Ambrose Equation Ambrose et a1.1*6,7330 advocate an equation in which vapour pressure is expressed as a logarithmic function of a series of normalized Chebyshev polynomials in temperature, s-I where E , k ) is the Chebyshev polynomial in x of order s and with Tmax and Tmin as temperatures just above and below the respective extremities of the T range. Eqn (4) offers two powerful advantages in the numerical analysis of vapour- pressure data. First, use of normalized, orthogonal polynomials obviates ill-conditioned properties associated with the regression of higher-order power series in T,7, 34p37 par- ticularly since x is normalized over the interval [ - 1, 1].36*37 Secondly, as Ambrose et al.7 note, the coefficients of these orthogonal functions in T cannot i n t e ~ a c t .~ ~ - ~ ~ 38-40 according to eqn (4) with T, = 562.5 K, Tmin = 294.0 K. A m b r o ~ e l . ~ ~ analyses the reference data1v2 in similar fashion with T,,, = 563 K, Tmin = 285 K, and quotes seven coefficients. A comparison of these with values derived here for four- and five-parameter fits of the reference data is given in table 2. Indicative of orthogonalized polynomial regression, coefficients from Ambrose's seventh-order fit overlap with corresponding Ambrose et aL7 treat the benzene vapour-pressure data of several t Using eqn (3) as an example, Ambrose et a1.5 report an improved regression procedurez2 for vapour-pressure equations which utilizes three constraints and the M a r q ~ a r d t ~ ~ algorithm for non-linear regression.With this method they predict p , from T, and vapour pressure for 52 substances, including ben~ene.~ The corresponding regression coefficients, however, do not appear to be available for comparison.'.2712 Assessment of Vapour-pressure Equations ones in both five-parameter fits. Also, within standard error limits, corresponding coefficients for the four- and five-parameter fits of Ambrose’s data’ overlap, and very nearly overlap for the data of Scott and Osborn.2 Inspection of the standard errors of estimate in table 2, however, clearly shows that both our four- and five-parameter fits are superior to the seven-parameter fit.The marked discrepancies in this respect are not easily reconciled, particularly since the orthogonality of the polynomials alleviates coefficient interaction and presumably en- sures the slow rise of condition number with increasing The explanation of this anomaly may lie in differences between the regression algorithms or in calculation precision (see above). Finally, we note that based on the F test, the fourth-order fits for both reference data sets give the optimum number of parameters. The Scott-Osborn Equation Scott and Osborn2 have developed two vapour-pressure equations, one for the entire liquid range and another appropriate to a limited T range.The latter is the result of two substantial improvements in the reduced form of the Frost-KalkwarPl equation, wherein p , and the implicit term d(AaH)/dT are taken as functions of both K and w, the acentric factor.,, For normal, quasi-normal and abnormal fluids over a limited T range, Scott and Osborn recommend lnp, = A+B/T,-3.013 In T,+5.512 T,-3.294 T,2 + D( - 62.646 In T, + 77.392 T,) - 19.424 ETf +O. 176p,exp[( 1.65 +0.8 E ) / T , -0.9 4. ( 5 ) The numerical constants in eqn ( 5 ) are related to its initial development for normal fluids (n-alkanes), and A, B, D and E are parameters specific to the fluid of interest, with E identified as w. For use in a straightforward manner, we have recast the equation as lnp, = c,+c,/T,+c, In T,+c3 T,-(3.294+ 19.424m)T; +0.176prexp[(1.65+0.8w)/T,-0.9w].( 6 ) From values of A, B, D and E reported by Scott and Osborn2 for eqn (9, we have generated corresponding values for co, c,, c, and c3 appropriate to eqn (6). These are given in table 3, where the results of Scott and Osborn are compared with ours for regressions of the reference data.1*2 Our four-parameter fits for both reference data sets give nearly identical coefficients, which is consistent with the observation that the reference data sets differ only s1ightly.l From the standard errors of estimate in table 3, the reference data of Scott and Osborn appear to be equally well represented by their coefficients and ours. Table 3 also shows the results for five-parameter regressions of the reference data.We have attempted to expand eqn (6) to five parameters in two ways; first, by substitution of a parameter (c,) for (3.294 + 19.424 w), the fixed coefficient of T;, and secondly, by addition of the term c, T:. The latter proved to be the more effective, but application of the F test to the results in table 3 shows that expansion to a term in T: is unwarranted for the reference data. The Cox Equation The used by Chao et aL4, to the more reliable form in reduced variables, expressed by equation may be delineated in various ways, from the simple form recently where lnp, = A(l- T;l) 1nA = C diTFi. Q i=OP. D. Golding and W. D. Machin 2713 Table 3. Regression parameters for representations of benzene vapour-pressure data by the Scott-Osborn equationa data set IIb data set Ib parame terb this workC Scott-Osbornd this workC - loco 37.897 4 - + 90.41 8 7 -C1 13.074 5 f 2.393 0 -cz 19.2469 f 10.675 1 c3 23.226 2 & 13.3669 1 oc, 1.230 5 k 20.577 9 a/Pab 1.84 43.302 8 f 2.439 9 13.217 4 f 0.1 42 9 19.8847 f 0.477 0 24.025 2 f 0.397 1 71.6134 & 3.9 14.7574 k0.14 23.391 9 f0.6112 30.687 8 f 0.801 9 1.83 2.75 56.95 1 9 & 75.267 9 1 3.590 4 f 2.140 7 21.526 6 f 9.242 6 26.044 8 & 1 1.201 6 & 16.157 1 2.50 - 2.959 0 43.169 5 f 1.955 6 13.1988 f0.1261 19.8350 & 0.407 8 23.993 8 f 0.328 8 2.52 a Eqn (6).T, = 562.16 K, see footnote, table 1 ; p , = 4898 kPa, after Ambrose, cf ref. (l), (2), (4), ( 5 ) , (7), (29), (30) and (42); o = 0.209, ref. (2) and (29)’ also see below. T, = 520 K, p , = 2956.0 kPa, o = 0.3273763, c, = A , c, = B, c, = -(3.013+62.646 See footnotes, table 1.D), C, = (5.512+77.392 0). Scott and Osborn2 state that eqn (7) gives a reasonably good interpolation of vapour- pressure data over a moderate T range when n = 1 and i > 2, but that the extrapolative properties of the function are ‘ abominably poor ’. To provide an analytic equation which gives a satisfactory representation of vapour-pressure data over the entire liquid range, Scott and Osborn have substantially improved eqn (7) by taking ‘n’ as an adjustable parameter. With this modification, these authors have regressed a composite set of benzene vapour pressures compiled from several sources2’ 29* 38-40* 4 5 9 46 for the entire liquid range. Their results are compared with ours for the reference data in table 4.From the statistical results, the eight coefficients reported by Scott and Osborn represent their own data2 better than those of Ambrose,’ but not as well as our four- and five-parameter fits in either case. Application of the F test to these fits shows the fifth parameter is null. The corresponding coefficients of the two four-parameter fits overlap well within the limits of their standard errors. Finally, we note that n < 1 for these fits, a fact in disagreement with the comments of Scott and Osborn.2 A Modified Clarke-Glew Equation Clarke and Glew’ have developed a general equation to represent the temperature dependence of reaction equilibria, viz. R l n K p = - L + A H g *‘* 0 (A --- ;)+ACE@ [;-1+ln(g)] where Kp is the equilibrium constant, 0 is a reference temperature, and AG;, AH: and the successive derivatives of AH: with respect to Tare standard (molar) thermodynamic quantities for the process with respect to 0 at a fixed pressure, pa.2714 Assessment of Vapour-pressure Equations Table 4.Regression parameters for representations of benzene vapour-pressure data by the Cox equationa data set Ib data set IIb parame terb Sco tt-0s bornc this workd Scott-Osborn" this workd n do -4 dz -4 4 -4 4 a/Pab 1.574414 1 f 0.33 2.340 184 f 0.16 2.9 13 768 f 0.68 8.389 532 f 1.3 14.508 140 f 2.2 15.146 082 k 3.5 8.568 283 - + 2.9 2.023 096 f 0.95 5.47 1.072 98 & 1.039 12 2.366 5 1 f0.572 14 1.61839 f 0.950 79 1.662 86 f 0.3 19 65 0.51942 f 0.719 72 0.661 48 f 0.064 77 2.69408 f 0.127 51 1.980 19 k0.26449 1.18845 0.133 41 1.84 1.98 1 S74414 1 - + 0.33 2.340 184 f0.16 2.9 13 768 f 0.68 8.389 532 f 1.3 14.508 140 f 2.2 15.146082 f 3.5 8.568 283 f 2.9 2.023 096 f 0.95 3.36 0.58 1 56 0.628 98 f 8.480 00 f 0.063 86 2.8 15 75 2.760 38 f 9.570 04 f 0.148 33 2.10402 2.1 16 16 f7.22839 f0.31045 1.030 96 1.256 04 f49.74020 f0.15928 & 32.973 09 0.15776 - 2.54 2.42 a Eqn (7).and p , constrained to 4882.8 kPa, ref. (2). kPa, see footnote, table 3. See footnotes, table 1. Coefficients for a composite data set with T, = 562.06 K T, = 562.16 K, see footnote, table 1 and p , = 4898 Numerous authors have recently used the Clarke-Glew equation to represent vapour- pressure data. For instance, de Kruif and coworkers'o-ls have recast the left-hand side of eqn (8) as R In (p/pe) to represent the temperature dependence of vapour pressures for substances of low volatility.Implicit in the use of standard-state designations is the approximation that the vapour pressures approach ideality. While this approximation may be valid for low pressure, it cannot be justified here for the real-gas behaviour of benzene vapour. Hence, we propose the following modifications of eqn (8) to represent the temperature dependence of vapour pressures : (9) The standard free-energy change is now properly identified through the R In po term by - A:d G$/O = R lnf,/pe = R (lnp, + In yo - lnpe) (10) where the standard reference pressure of the hypothetical, ideal gas, pe, is taken as 101.325 kPa, fo is the vapour fugacity at 0, and yo is the fugacity coefficient.Thermo- dynamic coefficients from regressions of the reference data according to eqn (9) are reported in table 5 . Based on the F test only four parameters are necessary to represent adequately the reference data and, within the standard error limits, the thermodynamic regression parameters are identical for both reference data sets. The extrapolative properties of eqn (9) appear satisfactory. With 0 = 298.150 K,P. D. Golding and W. D. Machin 2715 Table 5. Thermodynamic coefficients for the vaporization of benzene from the regression of reference vapour-pressure data according to a modified Clarke-Glew equationa parame terb data set Ib data set IIb PCWa 12.6925 +0.001 1 AH,/kJ mol-' 34.1164 & 0.007 9 -AC,,JJ K-' mol-' 47.084 7 f 0.478 8 102(d AC,/dT)./J KP2 mol-' 27.222 7 f 1.203 0 u/Pab 1.87 12.693 0 k0.0024 34.1130 f0.0117 47.038 4 f0.5249 27.336 3 f 1.039 3 2.50 a Eqn (9) with 0 = 298.150 K and R = 8.31441 J K-'mol-'.See footnotes, table 1. Table 6. Extrapolation of reference benzene vapour-pressure dataa no. of T = 298.15 K T = 278.67 K" equation parametersb p,,JkPa PCalJkPa 3 4 12.693 1 4.789 2 5d 12.6926 4.784 5 4 4 12.693 1 4.788 4 5d 12.692 5 4.784 8 5 4 12.6924 4.784 1 7 4 12.692 8 4.783 5 9 4 12.692 5 4.783 8 a Set 2/1968, ref. (1). Coefficients are reported in tables 1-5, respectively. Triple point, ref. (47). While only four co- efficients are justified in fitting the data, five coefficients appear to give the more reliable extrapolation. extrapolation of the reference data to = 0.7 yields an acentric factor, cr) = 0.2094, in excellent agreement with literature value^.^'^^ Similar extrapolations to T, = 562.16 K give pc = 4895 kPa from Ambrose's data' and pc = 4905 kPa from Scott and Osborn's data.2 These values agree remarkably well with p , = 4898f5 kPa reported by Ambrose,1~4*5+7~29~30 particularly since a 'reversal of curvature ' 5 9 39 occurs in In p us.T-', ca. = 0.85, a point well beyond the T range of the data. Extrapolation of Ambrose's data' to lower temperatures using eqn (9) gives values close to those from eqn (3), (4), (6) and (7), cf. table 6. Summary We have examined five modern vapour-pressure equations to determine the coefficients for each which best represent two sets of benzene reference data. From our analyses the following points are important.(1) Based on the F test (null hypothesis, 99 % confidence level), the best represen- tations of the reference data are given, without exception, by four-parameter fits to the vapour-pressure equations. (2) Four-parameter extrapolations of the reference data using the Scott-Osborn and2716 Assessment of Vapour-pressure Equations the modified Cox and Clarke-Glew equations give consistent results, but a fifth, less reliable parameter is required to obtain similar results using the Wagner and Ambrose equations (see table 6). (3) Of the two sets of reference benzene vapour pressures, Ambrose’s (set 2/1968)’ data give the more consistent fits to each of the vapour-pressure equations. (4) The Scott-Osborn equation and our form of the Clarke-Glew equation give slightly better representations of Ambrose’s reference data than the Cox equation, which in turn represents these data better than the Ambrose and Wagner equations.References 1 D. Ambrose, J , Chem. Thermodyn., 1981, 13, 1161. 2 D. W. Scott and A. G. Osborn, J. Phys. Chem., 1979, 83, 2714. 3 P. D. Golding and W. D. Machin, J. Chem. Soc., Faraday Trans. I , 1987, 83, 2719. 4 D. Ambrose, J. Chem. Thermodyn., 1978, 10, 765. 5 D. Ambrose, J. F. Counsell and C. P. Hicks, J. Chem. Thermodyn., 1978, 10, 771. 6 D. Ambrose and R. H. Davies, J. Chem. Thermodyn., 1980, 12, 871. 7 D. Ambrose, J. F. Counsell and A. J. Davenport, J. Chem. Thermodyn., 1970, 2, 283. 8 D. Ambrose, J. Chem. Thermodyn., 1986, 18, 45. 9 E. C. W. Clarke and D.N. Glew, Trans. Faraday Soc., 1966, 62, 539. 10 C. G. de Kruif and C. H. D. van Ginkel, J. Chem. Thermodyn., 1977, 9, 725. 11 C. H. D. Calk-vanGinke1, G. H. M. Calis, C. W. M. Timmermans, C. G. deKruifand H. A. J. Oonk, 12 C. G. de Kruif, T. Kuipers, J. C. van Miltenburg, R. C. F. Schaake and G. Stevens, J. Chem. Thermo- 13 C. G. de Kruif and J. G. Blok, J. Chem. Thermodyn., 1982, 14, 201. 14 C. G. de Kruif, R. C. F. Schaake, J. C. van Miltenburg, K. van der Klauw and J. G. Blok, J. Chem. 15 C. G. de Kruif, J. C. van Miltenburg and J. G. Blok, J. Chem. Thermodyn., 1983, 15, 129. 16 P. J. van Ekeren, M. H. G. Jacobs, J. C. A. Offringa and C. G. de Kruif, J. Chem. Thermodyn., 1983, 17 M. H. G. Jacobs, P. J. van Ekeren and C. G. de Kruif, J. Chem. Thermodyn., 1983, 15, 619.18 H. G. M. de Wit, J. C. van Miltenburg and C. G. de Kruif, J. Chem. Thermodyn., 1983, 15, 651. 19 W. E. Wentworth, J. Chem. Educ., 1965, 42, 96. 20 W. E. Deming, Statistical Adjustment of Data (Wiley, New York, 1943). 21 D. A. Brandreth, J. Chem. Educ., 1968, 45, 657. 22 S. D. Christian, E. H. Lane and F. Garland, J. Chem. Educ., 1974, 51, 475. 23 E. F. Meyer, Anal. Chem., 1982, 54, 1878. 24 W. S. Dorn and D. D. McCracken, Numerical Methods with Fortran ZV Case Studies (Wiley, New 25 B. W. Arden and K. N. Astill, Numerical Algorithms : Origins and Applications (Addison-Wesley, 26 W. Wagner, J. Ewers and W. Pentermann, J. Chem. Thermodyn., 1976, 8, 1049. 27 W. Wagner, A New Correlation Method for Thermodynamic Data Applied to the Vapour-pressure Curve of Argon, Nitrogen and Water, ed.J. T. R. Watson (IUPAC Thermodynamic Tables Project Centre, Imperial College of Science and Technology, London, 1977). J. Chem. Thermodyn., 1978, 10, 1083. dyn., 1981, 13, 1081. Thermodyn., 1982, 14, 791. 15, 409. York, 1972), p. 338. Reading, Mass., 1970), pp. 172-88, 240-3, 273-6. 28 W. Wagner, Cryogenics, 1973, 13, 470. 29 D. Ambrose, B. E. Broderick and R. Townsend, J. Chem. Soc. A, 1967, 633. 30 D. Ambrose, Pure Appl. Chem., 1977, 49, 1437. 31 F. D. Rossini, J. Chem. Thermodyn., 1970, 2, 447. 32 C. P. Hicks, The Constrained Fitting of Vapour Pressures, NPL Report Chem. 77 (Division of Chemical Standards, National Physical Laboratory, Teddington, England, 1978). 33 D. W. Marquardt, J. Soc. Znd. Appl. Math., 1963, 11, 431. 34 A. Ralston, A First Course in Numerical Analysis (McGraw-Hill, New York, 1965), pp. 271-306. 35 B. Carnahan, H. A. Luther and J. 0. Wilkes, Applied Numerical Methods (Wiley, New York, 1969), 36 C. de Boor and G. H. Golub, Recent Advances in Numerical Analysis (Academic Press, New York, 37 G. A. Watson, Approximation Theory and Numerical Methods (Wiley, Chichester, 1980), pp. 106-8. 38 J. F. Connolly and G. A. Kandalic, J. Chem. Eng. Data, 1962, 7 , 137. 39 P. Bender, G. T. Furukawa and J. R. Hyndman, Znd. Eng. Chem., 1952, 44, 387. 40 American Petroleum Institute Research Project 44 (loose-leaf data sheets extant, 1969) (Thermodynamics pp. 574-5. 1978), pp. 45-72. Research Center, Texas A & M University, College Station, Texas).P . D. Golding and W. D. Machin 2717 41 A. A. Frost and D. R. Kalkwarf, J. Chem. Phys., 1953, 21, 264. 42 A. P. Kudchadker, G. H. Alani and B. J. Zwolinski, Chem. Rev., 1968, 68, 659. 43 K. S. Pitzer, D. Z. Lippmann, R. F. Curl Jr, C. M. Huggins and D. E. Petersen, J. Am. Chem. SOC., 44 J. Chao, C. T. Lin and T. H. Chung, J. Phys. Chem. Ref. Data, 1983, 12, 1033. 45 A. W. Jackowski, J. Chem. Thermodyn., 1974, 6, 49. 46 G. D. Oliver, M. Eaton and H. M. Huffman, J. Am. Chem. SOC., 1948, 70, 1502. 47 J. Chao, Key Chemicals Data Books, Benzene (Thermodynamics Research Center, Texas A 8z M 1955, 77, 3433. University, College Station, Texas, 1978), p. 1. Paper 611562; Received 31st July, 1986

ISSN:0300-9599    

DOI:10.1039/F19878302709

出版商:RSC    

年代:1987

数据来源: RSC

摘要:

J. Chem. SOC., Faraday Trans. 1, 1987, 83 (9), 2719-2726 The Vapour Pressure of Benzene Part 2.-Saturated Vapour Pressures from 279 to 300 K Peter D. Golding* and William D. Machin Chemistry Department, Memorial University of Newfoundland, St John 's, Newfoundland, Canada A l B 3x7 An apparatus for precise, static measurements of vapour pressure in the range 1-100 mmHg is described. Vapour pressures of benzene are reported from 279 to 300 K. These are shown to be continuous and consistent with values extrapolated from reference data. Over the past decade there has been renewed interest in vapour pressure studies for a variety of While the relative merits of comparative ebulliometry5* and static methods7-' have been thoroughly discussed, we note that accurate ebulliometric meas- urements reported for vapour pressures in the atmospheric4 region (1-200 kPa) are not extensive below 10 kPa.l9 2 y lo The first aim of the present work, which is twofold in its ob- jectives, is the description of an automated apparatus and its use in accurate, static meas- urements of vapour pressure in the range 1-100 mmHg.? IUPAC recommendationsl0 have established vapour pressures of certain pure substances as reference standards.One of these is benzene.1i2,10 As the second objective of this work we report the vapour pressure of benzene from 279 to 300 K, the lower extremity of accepted reference data. '* Experimental A certified reference sample of benzene1 was sublimed under vacuum from the break- seal ampoule in which it was supplied into a reservoir containing dehydrated (in vacuo, 473 K) silica gel.The benzene was dried over the silica gel for ca. 20 h, and then sublimed under vacuum to a reservoir on the storage line. Prior to measurements on ca. 1-2 cm3 of the benzene, the entire sample was degassed by sublimationll and by several freeze-thaw cycles in vacuo.12 The apparatus, shown without accessories in fig. 1, is a high-vacuum system con- structed of glass and stainless-steel valves (Nupro, type SS-4H). The assembly is mounted in an insulated air bath maintained at 323.15 k0.03 K. Two sample flasks extend below the air bath into a well-stirred, constant-temperature bath. A bar magnet mounted on the stirrer shaft activates glass-encased magnets in each flask to provide sample stirring. The temperature of the bath can be regulated to better than k 1 mK for extended periods.The arrangement of the various electronic components in the apparatus is illustrated schematically in fig. 2. These devices are on a Hewlett-Packard (HP) IEEE bus system controlled by a microcomputer (HP 86A) and a data acquisition/control unit (HP 3497A). The microcomputer can initiate pressure (p), temperature (7') measurements, record the data on magnetic disk (HP 9130) and as printed copy (HP 82905B), upload data to a minicomputer (VAX 11/780) for processing and download the results. A recently recalibrated8 platinum resistance thermometer (Tinsley, model 5 1875AB) is situated between the sample flasks. Ice-point determinations with the thermometer t 1 mmHg = 101.325/760 kPa. $ Division of Chemical Standards, National Physical Laboratory, Teddington.9 Physics Division, National Research Council of Canada, Ottawa, Canada. 27192720 Benzene Saturated Vapour Pressures Fig. 1. A schematic diagram of the vapour pressure apparatus; A, air bath; B and C, 100 and 10 mmHg pressure sensors, respectively; D, to high vacuum; E, to purification and storage line; F, sample flasks; G, constant-temperature bath; V, valves. showed no significant change over the course of experimentation. Temperature is measured by the resistance comparison method13 using a standard 1 kR resistor (Leeds and Northrup, 4035B) in conjunction with the platinum resistance thermometer. The standard deviation in temperature measurement, ST, is ca. 1-2 mK. Two pressure sensors (MKS Instruments, type 315BH; 100 and 10 mmHg) are used to measure pressures.Corrections for atmospheric leakage and for the non-linearity of sensor output, taken from the manufacturer's calibration, are applied to each measure- ment. The rate of leakage into the system is linear with time and a function of bath temperature, such that 770 Ink = -14.89-- T where k/kPa s-l is the leak rate constant. If Sp is taken as the sum of the uncertainties in measurement precision, sensor calibration and leak rate, for a single measurement 6 p / p is (5-10) x lou5. We noted that the slope of the calibration of sensor voltage to pressure for the 100 mmHg head was offset, giving an effect similar to that reported by Ambrose et a1.12 Prior to measurements, the offset was corrected by adjustment of the T compensator (MKS multiplexer) so that the vapour pressure of benzene at 298.150 K was consistently observed as 12.692 56 +O.OOO 12 kPa over 36 separate, consecutive measurements.This value is selected as a reference point on the basis of the extrapolated values reported in table 6, part 1 of this series.14P. D. Golding and W. D. Machin HP 86A COMPUTER * * * PRINTER 272 1 DISC DRIVE VAX 11/780 COMPUTER VOLTMETER DATA PLATINUM AQUISITION/ - RESISTANCE CONTROL UNIT THERMOMETER - Results and Discussion The apparatus lends itself to two different techniques (methods I and 2) for the de- termination of vapour pressures. Method 1 employs equilibration of the sample at several temperatures in the range of measurement. At each temperature vapour pressures are sampled hourly until ST < p for 10 successive measurements.This method has the advantages that the sample is degassed and the sensor zeroed before each measurement, hence the measurements are not significantly affected by atmospheric leakage or electronic drift. The principal disadvantage of this method is the lengthy period required to change temperature and restore equilibrium. Vapour pressures meas- ured using method 1 are compared in table 1 with values extrapolated from the refer- ence data of Ambrose (set 2/ 1968)l using five vapour-pressure eq~ati0ns.l~ The measured and calculated values rarely differ by > 1 Pa and in no case is the difference > 0.03 %. The observed vapour pressures are in closest agreement with reference data extrapolated using the modified Clarke-Glew equation :14 1 mK and Sp < (2) F A R 1 YO2722 Benzene Saturated Vapour Pressures Table 1.A comparison of benzene vapour pressures measured by method 1 with extrapolated reference data“ calculated pressures, p,,,,/kPa ~ T / K p,,,/kPa Wagnerb 279.002 279.502 280.002 280.501 281.001 28 1.502 28 1.999 282.500 282.999 283.501 284.003 284.50 1 284.996 285.500 285.999 286.494 28 6.999 287.499 287.994 288.500 289.002 289.500 290.001 290.50 1 290.999 29 1.499 292.002 292.500 293.000 293.498 294.000 294.500 294.999 295.500 296.000 296.500 297.00 1 297.50 1 298.001 298.499 298.999 299.500 a/Pag 4.871 5.004 5.141 5.280 5.423 5.570 5.718 5.871 6.027 6.187 6.351 6.5 15 6.683 6.860 7.037 7.2 16 7.404 7.593 7.784 7.984 8.187 8.391 8.602 8.817 9.035 9.259 9.487 9.720 9.957 10.199 10.446 10.698 10.954 11.217 1 1.483 11.756 12.033 12.318 12.605 12.899 13.198 13.505 - 4.871 5 .d 5 5.141 5.281 5.424 5.570 5.718 5.871 6.027 6.187 6.351 6.5 17 6.685 6.860 7.038 7.2 17 7.404 7.594 7.785 7.985 8.187 8.392 8.603 8.8 17 9.035 9.259 9.488 9.720 9.957 10.198 10.446 10.698 10.954 11.216 1 1.484 11.756 12.034 12.317 12.605 12.898 13.198 13.504 0.917 Ambrosec 4.872 5.005 5.142 5.28 1 5.424 5.570 5.718 5.871 6.027 6.187 6.351 6.517 6.685 6.860 7.038 7.217 7.405 7.594 7.785 7.985 8.187 8.392 8.603 8.817 9.035 9.259 9.488 9.720 9.957 10.198 10.446 10.698 10.954 1.216 1.483 1.756 2.034 2.317 2.605 2.898 3.198 13.504 1.020 Scott- Osbornd 4.87 1 5.004 5.141 5.280 5.423 5.569 5.7 18 5.871 6.026 6.186 6.350 6.516 6.684 6.860 7.037 7.2 17 7.404 7.593 7.784 7.984 8.187 8.392 8.602 8.816 9.034 9.258 9.487 9.7 19 9.956 10.197 10.445 10.697 10.953 11.215 1 1.482 1 1.755 12.033 12.316 12.604 12.897 13.197 13.503 0.874 Clarke- COXe Glew f 4.870 5.004 5.140 5.280 5.423 5.569 5.717 5.870 6.026 6.186 6.350 6.516 6.684 6.860 7.037 7.2 17 7.404 7.593 7.785 7.985 8.187 8.392 8.603 8.8 17 9.035 9.258 9.488 9.719 9.957 10.198 10.446 10.698 10.954 11.216 1 1.484 1 1.756 12.034 12.317 12.606 12.899 13.198 13.504 0.73 1 4.871 5.004 5.141 5.2W 5.423 5.569 5.718 5.871 6.026 6.186 6.350 6.516 6.685 6.860 7.037 7.217 7.404 7.593 7.785 7.985 8.187 8.392 8.603 8.8 17 9.035 9.258 9.488 9.719 9.957 10.198 10.446 10.698 10.954 1.216 1.483 1.756 2.034 2.317 2.605 2.898 3.198 13.504 0.698 “Set 2/1968, ref.(1). “Eqn. (4) and table 2, ref. (14). dEqn (6) and table 3, ref. (14). fEqn (9) and table 5,, ref. (14). g Standard error of estimate, a, is the root-mean-square deviation = p ( A ~ ) ~ / / ( n - m)]% where Ap is pobs-pcalc, n is the number of data and rn is the number of parameters. bEqn (3) and table 1, ref. (14). “Eqn (7) and table 4, ref, (14).P . D. Golding and W. D . Machin 2723 0 -1 Y -5 L Fig. 3. Pressure residuals us. temperature from eqn (2); (a) set 1, (b) set 2, (c) set 3, ( d ) set 4, (e) Scott and Osborn, ref. (2), (f) Ambrose, set 2/1968, ref. (1). The second method of measurement, method 2, allows the temperature of the sample to increase or decrease slowly (0.19-0.26 mK s-l), and vapour pressures are measured at appropriate intervals (ca.0.1 K). The advantage of this method is the determination of a large number of vapour pressures over small temperature intervals. Over extended periods, however, atmospheric leakage can become significant at lower pressures. One of three sets of benzene vapour pressures measured using method 2 is reported in table 2. The other sets are in close agreement.? The benzene vapour-pressure data reported here, set 1 from method 1 and sets 2-4 from method 2, have been regressed according to the five vapour-pressure equations discussed in part 1.14 The results using the Wagner, Ambrose, Scott-Osborn and modi- fied Cox equations show that the relative order of 'goodness of fit', one data set to another, is the same as that expressed by the standard errors of estimate reported in table 3 for representation by eqn (2).Also typical of these regressions are the difference plots of Ap/Pa against T/K based on the results in table 3 as shown in fig. 3. From the standard errors of estimate for these regressions and their graphic description, typified in fig. 3, two observations are noteworthy. First, a comparison of results for method 1 and method 2 shows that method 2 yields the more precise results. Secondly, for the data considered here, both of these static methods apparently measure vapour pressures with more precision than the comparative ebulliometric techniques used to determine the reference data. Measurement accuracy, nevertheless, relies upon the one-point reference of the apparatus to the reference data (see Experimental). For comparison, vapour pressures have been calculated at integer temperatures for each of the data sets using the five vapour-pressure eq~ati0ns.l~ For brevity, these are represented in table 4 by values calculated from the modified Clarke-Glew equation.Corresponding vapour pressures calculated using the Wagner, Ambrose, Scott-Osborn and modified Cox equations are not appreciably different from those in table 4; 71 % are t Available from the authors upon request. 90-22724 Table 2. Benzene vapour pressures (set 2) measured by method 2 278.700 279.003 279.306 279.604 279.905 280.207 280.503 280.805 281.103 28 1.405 28 1.702 282.004 282.303 282.605 282.907 283.201 283.507 283.804 284.107 284.406 284.702 285.004 285.305 285.603 28 5.905 286.201 286.503 286.802 287.104 287.405 287.704 288.001 288.302 288.605 288.905 289.208 289.505 289.807 290.106 290.406 290.707 29 1.007 291.302 291.604 29 1.904 292.207 292.507 292.806 293.101 293.404 293.705 294.004 294.301 294.604 294.903 295.203 295.504 295 304 4.790 4.870 4.95 1 5.03 I 5.1 13 5.197 5.280 5.366 5.452 5.540 5.628 5.718 5.809 5.902 5.996 6.090 6.187 6.283 6.383 6.483 6.583 6.686 6.790 6.895 7.002 7.109 7.219 7.330 7.442 7.556 7.672 7.787 7.905 8.026 8.147 8.271 8.394 8.520 8.647 8.775 8.906 9.038 9.169 9.306 9.442 9.582 9.722 9.864 10.005 10.152 10.300 10.448 10.596 10.750 10.904 I 1.060 11.218 1 1.378 278.802 279.104 279.406 279.704 280.005 280.307 280.607 280.906 28 1.207 28 1.503 281 305 282.106 282.403 282.705 283.004 283.303 283.606 283.906 284.204 284.502 284.803 285.104 285.404 285.702 286.003 286.302 286.603 286.903 287.204 287.504 287.803 288.102 288.405 288.705 289.003 289.304 289.604 289.904 290.203 290.506 290.803 291.103 29 1.406 291.703 292.006 292.305 292.605 292.903 293.203 293.505 293.805 294.103 294.403 294.705 295.004 295.307 295.602 295.903 4.817 4.897 4.978 5.058 5.141 5.225 5.310 5.395 5.482 5.569 5.659 5.749 5.840 5.934 6.027 6.122 6.2 19 6.3 17 6.416 6.5 15 6.617 6.721 6.825 6.930 7.037 7.146 7.256 7.367 7.480 7.594 7.710 7.826 7.946 8.066 8.187 8.31 1 8.435 8.561 8.688 8.819 8.948 9.08 1 9.2 16 9.350 9.489 9.628 9.769 9.910 10.054 10.201 10.349 10.497 10.648 10.802 10.956 11.114 11.271 11.431 278.906 279.204 279.507 279.804 280.105 280.402 280.707 281.004 281.303 28 1.606 281.903 282.207 282.504 282.801 283.105 283.403 283.705 284.004 284.305 284.601 284.904 285.204 285.503 285.80 1 286.104 286.402 286.703 287.002 287.305 287.603 287.905 288.202 288.506 288.80 1 289.106 289.402 289.703 290.007 290.304 290.607 290.907 29 1.207 291.505 291.806 292.105 292.404 292.703 293.005 293.304 293.605 293.904 294.207 294.506 294.807 295.103 295.402 295.701 296.001 4.845 4.924 5.005 5.086 5.169 5.252 5.338 5.423 5.510 5.599 5.688 5.780 5.871 5.963 6.059 6.154 6.251 6.349 6.449 6.549 6.652 6.755 6.860 6.965 7.074 7.182 7.293 7.404 7.5 18 7.632 7.749 7.866 7.986 8.105 8.229 8.351 8.476 8.605 8.732 8.863 8.994 9.127 9.261 9.397 9.535 9.674 9.815 9.959 10.103 10.250 10.398 10.549 10.701 10.854 1 1.008 11.164 1 1.323 1 1.4842725 Table 2 (continued) 296.106 296.40 5 296.704 297.003 297.305 297.603 297.903 298.204 298.507 298.806 299.106 299.406 1 1.540 1 1.703 1 1.868 12.035 12.205 12.375 12.548 12.723 12.902 13.081 1 3.262 13.446 296.204 296.503 296.803 297.104 297.405 297.704 298.003 298.305 298.603 298.906 299.203 299.508 1 1.594 11.757 1 1.923 12.092 12.262 12.433 12.606 12.783 12.960 13.141 13.321 13.508 296.302 296.602 296.901 297.201 297.503 297.804 298.102 298.405 298.705 299.006 299.305 11.647 11.81 1 1 1.978 12.146 12.317 12.490 12.663 12.842 13.020 13.202 13.384 Table 3.Thermodynamic coefficients for the vaporization of benzene calculated from a modified Clarke-Glew equation" parameter set 1 set 2 set 3 set 4 P@/kPa 12.692 5 12.692 1 12.692 9 12.692 5 +0.0010 k0.0003 +0.0004 f0.0003 AH,/kJ mol-' 34.1176 34.1 129 34.1 14 5 34.101 9 f0.0143 f0.0044 f0.0056 k0.0038 AC,,JJ K-' mol-' 48.5692 49.630 1 50.023 4 50.8506 k 1.5139 k0.4606 f0.5843 f0.3985 a/Pab 0.621 0.289 0.392 0.286 "Eqn (2) with 0 = 298.150 K and R = 8.31441 J K-l mol-'.'See footnotes, table 1 Table 4. A comparison of interpolated benzene vapour pressuresa Scott- T / K set 1 set 2 set 3 set 4 Ambrose* Osbornc 279 280 28 1 282 283 284 285 286 287 288 289 290 29 1 292 293 294 295 296 297 298 299 300 4.870 5.140 5.423 5.718 6.026 6.349 6.686 7.037 7.404 7.787 8.186 8.602 9.035 9.486 9.956 10.445 10.954 1 1.483 12.033 12.605 13.199 13.815 4.870 5.139 5.422 5.7 17 6.026 6.348 6.685 7.037 7.404 7.786 8.185 8.601 9.035 9.486 9.956 10.445 10.954 1 1.483 12.033 12.605 13.198 13.815 4.869 5.139 5.421 5.717 6.026 6.348 6.685 7.037 7.404 7.786 8.186 8.602 9.035 9.487 9.957 10.446 10.955 1 1.484 12.034 12.605 13.199 13.816 4.870 5.140 5.422 5.7 17 6.026 6.349 6.686 7.037 7.404 7.787 8.186 8.602 9.036 9.487 9.957 10.446 10.955 1 1.484 12.034 12.605 13.198 13.815 4.870 5.140 5.423 5.718 6.027 6.349 6.686 7.038 7.404 7.787 8.186 8.602 9.035 9.487 9.957 10.446 10.954 1 1.483 12.033 12.605 13.199 13.815 4.870 5.140 5.422 5.717 6.026 6.349 6.686 7.037 7.404 7.787 8.186 8.602 9.035 9.487 9.957 10.446 10.954 1 1.483 12.033 12.605 13.199 13.815 aFrom eqn (2) with parameters from table 3.5, ref. (14). *Set 2/1968, ref. (1) with parameters from table "ata from ref. (2) with parameters from table 5, ref. (14).2726 Benzene Saturated Vapour Pressures identical, 28 YO differ by < 2 1 Pa and 1 YO are lower by < 2 Pa.Clearly, irrespective of which equation is employed, vapour pressures interpolated from the four data sets here are in excellent agreement with each other and with vapour pressures extrapolated from the reference data. Summary Saturated vapour pressures are reported for liquid benzene from 279 K to the lower extremity of reference data. These vapour pressures are coincident with values extrapolated from the reference data by means of five vapour-pressure equations, and hence provide a useful extension to the reference data. We take this as confirmation of both the bonafides of the apparatus and the validity of the two static methods of measurement. We thank Mr A. Earle for his assistance in producing the figures. References 1 D. Ambrose, J. Chem. Thermodyn., 1981, 13, 1161. 2 D. W. Scott and A. G. Osborn, J. Phys. Chem., 1979, 83, 2714. 3 D. Ambrose, J. Chem. Thermodyn., 1978, 10, 765. 4 D. Ambrose and R. H. Davies, J. Chem. Thermodyn., 1980, 12, 871. 5 S. Malanowski, Fluid Phase Equilibria, 1982, 8, 197. 6 Experimental Thermodynamics, Volume [ I : Experimental Thermodynamics of Non-reacting Fluids, ed. 7 A. G. Williamson, ref. (6), chap. 16. 8 M. M. Abbott, in Phase Equilibria and Fluid Properties in the Chemical Industry, ed. T. S . Storvick and 9 K. N. Marsh, in Chemical Thermodynamics, ed. M. L. McGlashan (Specialist Periodical Report, The B. Le Neindre and B. Vodar (Butterworths, London, 1975). S. I. Sandler (ACS Symp. Ser. 60, American Chemical Society, Washington, 1977), pp. 87-98. Chemical Society, London, 1978), vol. 2, pp. 145. 10 D. Ambrose, Pure Appl. Chem., 1977, 49, 1437. 11 T. N. Bell, E. L. Cussler, K. R. Harris, C. N. Pepela and P. J. Dunlop, J. Phys. Chem., 1968, 72, 12 D. Ambrose, I. J. Lawrenson and C. H. S. Sprake, J . Chem. Thermodyn., 1975, 7 , 1173. 13 J. V. Nicholas and D. R. White, Traceable Temperatures, DSIR Bulletin 234 (New Zealand Department 14 P. D. Golding and W. D. Machin, J. Chem Soc., Faraday Trans. I , 1987, 83, 2709. 4693. of Scientific and Industrial Research, Wellington, 1982), chap. 7. Paper 6/1563; Received 31st July, 1986

ISSN:0300-9599    

DOI:10.1039/F19878302719

出版商:RSC    

年代:1987

数据来源: RSC

摘要:

J . Chem. Soc., Faraday Trans. I , 1987, 83 (9), 2727-2734 Comparison between Heterogeneous and Homogeneous Electron Transfer in p-Phenylenediamine Systems Andrze j Kap turkiewicz f- and Walt her Jaenicke * Institut fur Physikalische und Theoretische Chemie der Universitat Erlangen- Niirnberg, Egerlandstrape 3, 8520 Erlangen, Federal Republic of Germany The one-electron oxidation of selected p-phenylenediamines to form the corresponding radical cations has been studied at a Pt electrode in dimethylformamide and acetonitrile solutions containing 0.1 mol dm-3 NaClO,. The standard redox potentials, the diffusion coefficients and the standard rate constants have been evaluated in the range between room temperature and the melting point of the respective solvent using cyclic voltammetry.It has been shown that the dynamics of solvent reorientation affects the heterogeneous electron-transfer rate, as opposed to the homogeneous process. The free energies of activation are much greater in the heterogeneous than in the homogeneous case. Both results are explained by the different shape of the activated complexes, consisting of one or two ellipsoidal molecules. Electron-exchange reactions are activated processes. The observed rate constant, k,, is related to the overall free-energy barrier, AG*, and the pre-exponential term, A , by k, = A exp (-AG*/RT). (1) According to the ‘ encounter pre-equilibrium ’ the formation of a precursor complex of the reactants (in homogeneous reactions) or of the system reactant-electrode (in heterogeneous reactions) precedes the activated electron transfer.With this assumption A is given by (2) where v, is the effective nuclear frequency factor (the frequency of surmounting the free- energy barrier in the classical high-temperature limit), u,, is the electronic transfer coefficient and Kp is the association constant of the precursor complex. Generally K p can be expressed by the Eigen e q ~ a t i o n . ~ Another expression for K p is found if it is assumed that the transfer takes place preferentially within a small range of distances &.6-8 Then for homogeneous reactions : (3) (4) where F is the mean particle radius, N is Avogadro’s constant and w(d) is the energy required to transfer the reacting particle from the bulk solution to the reaction site. In the electrochemical case w(d) is equivalent to the so-called ‘ Frumkin correction ’.v, may be approximated in the two-mode model usedg*10 by the mean frequencies of molecular vibration, v i , and solvent reorientation, v,. Generally two limiting cases are discussed: In the first the pre-exponential term is A = u,, V , K p Kp = 471.~~26~lV exp [ - w(d)/RT] K p = 6~ exp [ - w(d)/RT] and for heterogeneous reactions : t On leave from the Institute of Physical Chemistry of the Polish Academy of Sciences with an Alexander von Humboldt fellowship. 27272728 Electron Transfer in p- Phenylenediamine Systems controlled by inner vibrations of the reactant, whereas in the second it is controlled only by the dynamics of solvent reorientation via the longitudinal relaxation time, zL, of the given solvent.The latter is valid'' if P(A) = vi[Ai/(Ai + A,)]; exp (- Ai/4RT) > zL-l where Ai and A, are the inner and outer reorganization energies in the sense of Marcus's theory.l2<l3 In this case v, may be expressed as follows:'4-'6 (6) V , = z,i(no/ I 6 . n ~ ~ ) ; . If, however, the reaction rate is controlled by molecular vibrations3 v, = Vi[Ai/(Ai +A0)];. (7) The latter approximation is questionable and leads to pre-exponential terms much higher than observed." It has to be assumed that in this case the electronic transfer coefficient is small ( I C , ~ 6 1).18 Generally Ai as well as A. are different for homogeneous and heterogeneous reactions. Up to now the theories of electron-transfer reactions were tested for the heterogeneous case mostly from experiments at one temperature.To our knowledge only for some aquo- and amino- complexes in aqueous has the temperature dependence of electron-transfer kinetics in both homogeneous and heterogeneous cases been simultaneously studied. For p-phenylenediamines the homogeneous electron exchange has been studied extensively,"* 20* 21 but the corresponding heterogeneous reaction in dimethylformamide and acetonitrile only at one temperature22 and for unsubstituted p-phenylenediamine in different It was found that the solvent reorientation dynamics play an important role in the electrochemical case,23 whereas the homogeneous reaction is independent of 7,. The explanation of this problem was the purpose of this work. We have studied the first oxidation step of selected p-phenylenediamines (PPD), forming stable radical cations for a wide range of temperatures in dimethylformamide and acetonitrile.PPD - e- PPD'+ (8) Experimental Materials All amines used [p-phenylenediamine (PPD), N,N-dimethyl-p-phenylenediamine (DMPPD), N,N,N',N'-tetramethyl-p-phenylendediamine (TMPPD) and 2, 3, 5, 6-tetra- methyl-p-phenylenediamine (DAD)] were commercial products, purified by vacuum sublimation or distillation. Analytical-grade NaClO, was dried at 120 "C. Analytical- grade ferrocene (Fc) was used as received. Acetonitrile (ACN) and dimethylformamide (DMF) were dried and purified for electrochemical use in the conventional manner.24 Apparatus To obtain the transfer rate constant cyclic voltammetry was used. The measuring system for cyclic voltammetry was constructed from a Wenking VSG 72 voltage scan generator and a home-built potentiostat.The cyclic voltammograms were stored in a Nicolet 2020 digital oscilloscope. To compensate the ohmic drop a current-follower configuration with negative input impedance was ~ ~ e d . ~ ~ y ~ ~ The working electrode was a Pt disc with an area of 0.01 1 cm2 and was polished before each use with diamond paste. The counter electrode was a platinum wire and the reference electrode was an aqueous saturatedA . Kapturkiewicz and W. Jaenicke 2729 Table 1. Electrochemical parameters and diffusion coefficients D for oxidation of selected p- phenylenediamines at 20 "C D ks (dE/dT) solvent solute E"/V us. Fc/Fc+ /cm2 s-l /cm s-' /mV K-I DMF PPD - 0.28 9.1 x lob6 0.092 0.91 DMPPD -0.34 7.4 x 0.23 0.79 TMPPD - 0.29 10.9 x 0.19 0.54 DAD -0.37 10.8 x 0.080 1.10 ACN PPD -0.11 20.6 x 0.6" 1.21 a Extrapolated value.calomel electrode with an agar plug. An additional platinum wire was dipped in the solution and was connected via a 0.1 ,uF capacitor to the reference electrode. The role of this wire was to shunt the high-frequency components of the applied signal from the reference electrode. 27 All potentials at room temperature were also referred to ferrocene/ ferricinium (Fc/Fc+). Procedure The standard heterogeneous rate constants, k,, were evaluated from the observed differences between anodic and cathodic peak potentials AE of the cyclic voltammograms using the relationship of Nico1son.28 AE could be measured with a precision of ca.2 mV for potential scan rates between 0.1 and 100 V s-' (depending on k,). The diffusion coefficients D and the standard redox potentials E" were also determined from cyclic voltammograms recorded at scan rates of 0.1-1 V s-l. The error limit of the electrochemical parameters was ca. 20 % for k,, 10 YO for D, and 5 mV for E". All measurements were carried out in solutions deaerated with pure argon at different temperatures > - 60 "C. The reference electrode was kept at room temperature (20 "C). The concentrations of supporting electrolyte (NaClO,) and reactants were 0.1 and 0.00 1 mol dm-3, respectively. The working electrode was immersed in the deaerated solution and cycled many times in the potential range f 0.2 V around the redox potential of the system studied.By this procedure reproducible results were obtained, although the surface state is not well defined. Results Dimethylformamide Solutions For all systems studied, current-potential curves with nearly equal anodic and cathodic peak currents were obtained. A summary of the evaluated electrochemical parameters (at 20 "C) is presented in table 1. The results agree very well with the literature data.22i23 With increasing temperature the standard redox potentials are shifted to more positive values (table 1). This indicates negative solvation entropies for the studied radical cations, but the effect is not large, only somewhat greater than for metallo~enes~~ and is close to the values for q u i n ~ n e s . ~ ~ It is concluded that the aromatic radical cations are relatively weakly solvated.The results indicate also that the association between radical cations and C10, anions is small. This is in agreement with the independence of the standard redox potentials of the concentration of the supporting electrolyte. 232730 Electron Transfer in p-Phenylenediamine Systems For DMF as solvent the energy of activation for the diffusion process is ca. 30% greater than the energy of activation for viscosity, as in the case of q ~ i n o n e s . ~ ~ Since the electrode reaction rates could be measured between - 60 "C and + 20 "C (21 3-293 K), the activation parameters could be obtained rather precisely. Ace tonitrile Solutions In this solvent all reactions studied were much faster than in dimethylformamide. Therefore the rate constants could not be measured at room temperature with the method used.Although the reactions were slower at low temperatures, precise measurements were only possible with PPD. For all other systems studied even at - 30 "C the rate constants exceeded 0.2 cm s-l. Since the melting point of 0.1 mol dm-3 NaClO, solutions lay between -50 and -60 "C, the useful temperature range was too small to measure the activation parameters precisely. Even for PPD it was impossible to obtain k, at 20 "C. This disagrees with the results of Pluschke22 and Opal10,~~ but their values k, = 0.17 cm s-l and k, = 0.22 cm s-l, respectively, are close to the limit of classical cyclic voltammetry. Therefore in ACN solutions only the PPD/PPD+ system could be measured with the required precision, and only kinetic data for this system will be discussed further. The temperature dependence of the other electrochemical parameters (D and P) can be interpreted in the same way as in DMF solutions.Discussion Heterogeneous Kinetics To determine the activation parameters exactly the temperature dependence of the pre- exponential factor has to be known. With the experimental values of A, (for DMF solutions ca. 100 kJ mol-l, see later) and calculated values of li (ca. 10 kJ mol-' at 293 K17720)t it is found from the inequality of Ovchinnikova'l" [eqn (5)] that P(A) > z;'. Therefore we tried to interpret the experimental results using eqn (6) and (4) with w(d) = 0 using the following expression for k,:29v32 k, = K,, drT;l(A,/ 16xRT)f exp [ - (A, + Ai)/4RT]. (9) Although in the above equations Ai and A, as well as z, are temperature dependent, to a first approximation ;li and A, may be assumed to be constant. This is allowed since in the heterogeneous case li is small compared with A,. Also the term (1 / n 2 - 1 / E ) in A, [cf.eqn (ll)] varies by only 3% within the temperature range used. If the temperature dependence of z, can be described as29 zL-' = A , exp (- HJRT) from eqn (9) a linear relationship between In (k, Ti) and 1 / T should be observedlwith a slope equal to (li/4 + A,/4 + H,) and an intercept equal to In A , K , ~ sr(A,/ 16;nR)Z. Dielectric relaxation data for DMF as well as for ACN are incomplete, but with the available it is possible to estimate A , and H L for both DMF and ACN. A, are 33.2 x 10l2 and 4.3 x 10l2 s-l, and H, are 4.6 and 4.2 kJ mo1-1 for ACN and DMF, respectively. In fig.1 In (k, Tf) is plotted us. 1 / T. Linear relationships with correlation coefficients always better than 0.99 are found. The experimentally obtained values of intercepts and slopes for all systems studied are presented in table 2. From the experimental slope the sum of li and lo can be obtained after subtraction -f In ref. (17) and (20) the calculated values of 1, for the homogeneous case have to be multiplied by 2; therefore for the heterogeneous Li the given values can be used.A . Kapturkiewicz and W. Jaenicke 273 1 lo3 KIT Fig. 1. In (k,Ti) as a function of T' for p-phenylenediamines studied in dimethylformamide (0) and acetonitrile (0). Temperature range 213-293 K.Table 2. Experimental kinetic parameters for electro-oxidation of selected p-phenylenediamines (2,/4) + (Ai/4) H , A, + A, A , K,, &(A,,/ 16nR)i solvent solute /kJ mol-' /kJ mol-' /cm s-' Ki ~~~~~~~~~ DMF PPD 32.5 113 10.3 x 105 DMPPD 26.3 88 2.0 x 105 TMPPD 29.0 99 5.1 x 105 DAD 30.6 106 4.7 x 105 ACN PPD 30.7 104 4.2 x los of HL. The calculated values of Ai (10 kJ mol-l at the mean temperature of the experiments20) are small compared with the experimental 1, of ca. 100 kJ mol-l. To calculate 1, the classical Marcus theoryl29l3 can be used, in which A0 is given as a function of the polarity parameter y = (l/n2- 1 / ~ ) of the solvent, depending on its refractive index It and dielectric constant E , and the geometric parameter g x (1/2)(1/F- 1/24) where F is the 'effective' radius of the reacting particle and d is the distance from the electrode surface when electron transfer occurs : 1, = (ei N / ~ Z E ~ ) (1 / n 2 - 1 / E ) (1 / f - 1 /24.(1 1) According to eqn (1 1) A, depends strongly on F and d. In the spherical approximation f can be calculated from the molar volume of the substances studied. Large values of 1, indicate that the image interaction of the reactant with the electrode can be neglected2732 Electron Transfer in p-Phenylenediamine Systems Table 3. Calculated kinetic parameters for electro-oxidation of selected p-phenylenediamines spherical model ellipsoidal model A , K , ~ dr(A,/ 16nR)i" solvent solute r/nm A,/kJ mol-' r/nm IJkJ mol-' /cm s-l Kf ~~~~ ~~~ DMF PPD 0.33 97 0.278 115 4.3 x 105 DMPPD 0.37 87 0.294 109 4.2 x 105 TMPPD 0.34 91 0.406 79 3.6 x 105 DAD 0.4 76 0.317 101 4.0 x 105 ACN PPD 0.33 111 0.278 131 3.5 x lo6 a Calculated with 2, from the ellipsoidal model and IC,, 6r = 60 pm.( d = 00) as was proposed by Hale.35 The values of r and Lo for the spherical approximation with d = co are given in table 3. If the molecule is approximated by an ellipsoid with the semi axes a > b > c, l / r is expressed byzo, 36 I / F = (a2 - c 2 ) : / ~ ( a , # ) where # = arcsin (a2 - c2)!/a; a = arcsin[(a2 - c2)/(a2 - b2)]! and F(a,$) is the elliptic integral of the first kind. The values of r and A. for this model (with the assumption d = co) are also given in table 3. The semiaxes are obtained from crystallographic data [see ref. (20)]. Lo for heterogeneous processes, calculated from both models, differ by less than ca.20% if the image charges are neglected (d+ co). In table 3 the calculated values of the pre-exponential factor are also given, calculated with Lo values from the ellipsoidal model and with values of K,,& equal to 60 pm.37 The agreement between theory and experiment (table 2) is satisfactory. For values of K,, 6r = 60 pm it can be assumed that the reaction is adiabatic for the closest approach of the reactant to the electrode surface ( K , ~ = 1).37*38 For interpretation the apparent standard rate constants k, have been used. This may be correct in view of the results presented in ref. (23). For the PPD system it was found that k, is nearly independent of the concentration of the supporting electrolyte.Moreover E" values (see table 2) are close to the estimated zero-change potential of the Pt electrode in perchlorate solutions [cf. ref (23) and references therein]. Therefore the measured values of k, can be taken as ' true' values, not influenced by the potential drop in the diffuse layer. Measured (table 2) and calculated (table 3) data of the pre- exponential and the exponential terms of k, correspond well. Comparison between Heterogeneous and Homogeneous Electron-transfer Kinetics The logarithm of the homogeneous electron self-exchange rate constant of p- phenylenediamines was found to be independent of z, but proportional to the solvent polarity parameter y. This can be discussed in terms of the classical Marcus model without considering solvent relaxation phenomena.17* 2oi 21 We assume that the different behaviour is connected with the structure of the activated complex in both cases, expressed by the differences in Li and in the geometric parameter g. Since two molecules are involved in homogeneous processes, L,(hom) = 2 A,(het) [in the present case at 298 K : L,(hom) = 20 kJ The geometric parameter for homogeneous processes is g = l / r - 1/2d, where 2d is the distance between the molecule centres. For spherical molecules 2d 3 2r and for ellipsoids 2d 2 2r, since the minimum distance is given by the smallest semiaxis, c. If the image interaction can be neglected [d(het) -+ GO] one obtains for spherical molecules g(hom) = g(het) z 1/2r. For ellipsoids, however, g(hom) may be much smaller than g(het), the minimum value being g(hom) M l/r- 1/2c.A .Kapturkiewicz and W. Jaenicke 2733 The experimental values of ;l,(hom) were ca. 40 kJ mol-l 2o for p-phenylenediamines, compared with 100 kJ mol-1 found for A,(het) (see table 3). With the rather small ;l,(hom) and Ai(hom) always greater than A,(het) it results from the inequality of Ovchinnikova [eqn (1 1 a)] that P(;l)het > P(IZ)hom.39 For p-phenylenediamines P(A)hom z z,', P(A)het < 7;'. The homogeneous electron exchange may therefore be just a borderline case, whereas in the heterogeneous reaction the solvent dielectric relaxation dynamics prevail. Conclusion It has been shown that the experimental results for the heterogeneous electron transfer in p-phenylenediamine systems can be discussed in terms of an 'encounter pre- equilibrium' model in which the pre-exponential term is determined by solvent reorientation dynamics.The larger value of Ai for homogeneous reactions explains the independence of electron-transfer kinetics on solvent reorientation dynamics in this case. For electron-transfer reactions it is generally expected that heterogeneous processes should be more likely to be controlled by dielectric relaxation properties of the solvent than homogeneous processes. A.K. thanks the Alexander von Humboldt Foundation for a scholarship. References 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 N. Sutin, in Inorganic Biochemistry, ed. G. L. Eichhorn (Elsevier, New York, 1973), vol. 2, chap. 19, p. 611. M. D. Newton and N.Sutin, Annu. Rev. Phys. Chem., 1984, 35, 457. N. Sutin, in Progress in Inorganic Chemistry, ed. S . J. Lippard (Wiley-Interscience, New York, 1983), vol. 30, p. 441. R. R. Dogonadze, A. M. Kusnetsov and T. A. Marsagishvili, Electrochim. Acta, 1980, 25, 1. M. Eigen, Z. Phys. Chem. N.F., 1954, 1, 176. R. A. Marcus, Int. J. Chem. Kinet., 1981, 13, 865. N. Sutin, Acc. Chem. Res., 1982, 15, 275. M. J. Weaver and J. T. Hupp, J. Electroanal. Chem., 1983, 152, 1. B. S. Brunschwig, C. Creutz, D. H. Macarthney, T. K. Sham and N. Sutin, Faraday Discuss. Chem. Soc., 1982, 74, 113. R. R. Dogonadze and Z. D. Urushadze, J. Electroanal. Chem., 1971, 32, 235. (a) M. Ya. Ovchinnikova, Russ. Theor. Exp. Chim., 1981, 17, 507; (b) L. D. Zusman, Chem. Phys., 1987, 112, 53. R.A. Marcus, Annu. Rev. Phys. Chem., 1960, 29, 21. R. A. Marcus, J . Chem. Phys., 1956, 24, 966. A. I. Burshtein and A. G. Kofman, Chem. Phys., 1979, 40, 289. L. D. Zusman, Chem. Phys., 1980, 49, 295. D. F. Calef and P. G. Wolynes, J. Phys. Chem., 1983, 87, 3387; J . Chem. Phys., 1983, 78, 470. G. Grampp and W. Jaenicke, J. Chem. SOC, Furaday Trans. 2, 1985, 81, 1035. W. Harrer, Ph.D. Thesis (Erlangen, 1986); W. Harrer, G. Grampp and W. Jaenicke, to be published. J. T. Hupp and M. J. Weaver, J. Phys. Chem., 1985, 89, 2795. G. Grampp and W. Jaenicke, Ber. Bunsenges. Phys. Chem., 1984, 88, 325. G. Grampp and W. Jaenicke, Ber. Bunsenges. Phys. Chem., 1984, 88, 335. P. G. Pluschke, Ph. D. Thesis (Erlangen, 1981). M. OpaHo, J. Chem. Soc., Faruday Trans. I , 1986, 82, 339. C. K. Mann, in Electroanalytical Chemistry, ed. A. J. Bard (Marcel Dekker, New York, 1969), vol. 3, C. Lamy and C. C. Herrman, J . Electroanal. Chem., 1975, 59, 1 13. D. Britz, J. Electroanal. Chem., 1978, 88, 309. C. C. Herrmann, G. G. Perrault and A. A. Pilla, Anal. Chem., 1968, 40, 1173. R. S. Nicholson, Anal. Chem., 1965, 37, 1351. T. Gennet, D. F. Milner and M. J. Weaver, J. Phys. Chem., 1985, 89, 2787. p. 57.2734 Electron Transfer in p- Phenylenediamine Systems 30 J. S . Jaworski, Electrochim. Acta, 1986, 31, 85. 31 T. Nagaoka and S . Okazaki, J. Phys. Chem., 1985, 89, 2340. 32 M. J. Weaver and T. Gennet, Chem. Phys. Lett., 1985, 113, 213. 33 K. Krishaji and A. Hausingh, J. Chem. Phys., 1964,41, 827. 34 S. J. Bass, W. 1. Nathan, R. M. Meighan and R. M. Cole, J. Phys. Chem., 1964, 68, 1463. 35 J. M. Hale, in Reactions of Molecules at Electrodes, ed. N. S . Hush (Wiley, London 1971), p. 243. ;6 E. D. German and A. M. Kusnetsov, Electrochim. Acta, 1981, 26, 1595. 37 J. T. Hupp and M. J. Weaver, J. Phys. Chem., 1984, 88, 1463. 38 G. Grampp, W. Harrer and W. Jaenicke, J. Chem. SOC., Faraday Trans. I , 1987, 83, 161. 39 G. Grampp, W. Harrer and W. Jaenicke, J. Electroanal. Chem., 1986, 209, 223, Paper 6/ 1666 ; Received 14th August, 1986

ISSN:0300-9599    

DOI:10.1039/F19878302727

出版商:RSC    

年代:1987

数据来源: RSC