摘要:

The rate of solvent extraction of chromium(III) from aqueous sulphuric acid solutions (containing 0.05 mol dm−3sulphate ion and 0.25 mol dm−3acetate buffer, ionic strength,I = 0.40 mol dm−3) with bis-(2-ethyl hexyl) phosphoric acid (HDEHP or H2A2) in benzene has been measured under various conditions. The rate of backward extraction measurement of Cr(III) from organic phase to aqueous phase is not possible due to the inert property of Cr(III)–DEHP chelate. The forward rate is found to be first-order w.r.t. Cr(III) concentration in the aqueous phase and HDEHP concentration in the organic phase. The order w.r.t. H+concentration varies from −1 to 1 over the pH range 1.5 to 5.25. The rate is found to decrease with increasing sulphate and nitrate ions concentrations in the aqueous phase. At (30 ± 1) °C, the rate expression, in the presence of sulphate, acetate, and nitrate ions, is found to be represented by:In the absence of the anions, the formation of CrHA22+intermediate complex (Cr(OH)2+ + H2A2(0) → CrHA22+ + H2O) is the rate determining step at all acidities. The effects of the anions on the rate are discussed.

ISSN:0008-4042    

DOI:10.1139/v79-490

出版商:NRC Research Press    

年代:1979

数据来源: NRC

摘要:

The oxidation of ascorbic acid (AH2) and hydroquinone (QH2) by photolytically generated HO2•radicals was studied over a broad range of pH. The rate constants of the following processes were obtainedanddepending upon two different possible mechanistic interpretations.

ISSN:0008-4042    

DOI:10.1139/v79-491

出版商:NRC Research Press    

年代:1979

数据来源: NRC

摘要:

The effect of an applied magnetic field on the fluorescence from γ-irradiated solutions of perfluorobiphenyl and perfluoronaphthalene has been measured in various solvents. In all the solvents used (cyclohexane, squalane, isooctane) the fluorescence intensity increases with increasing field and tends towards a plateau at high fields (>0.1 T). At low fields, the fluorescence enhancement is smaller for the perfluorocarbons than for the parent hydrocarbons, due to the larger electron–nuclear hyperfine coupling and broader spread of the hyperfine levels in the radical ions of the perfluorocarbons. At high fields the fluorescence enhancement is also smaller for the perfluorocarbons than for the parent hydrocarbons, indicating a larger relative proportion of prompt (field-independent) fluorescence for the perfluorocarbons than for the parent hydrocarbons.

ISSN:0008-4042    

DOI:10.1139/v79-492

出版商:NRC Research Press    

年代:1979

数据来源: NRC

摘要:

A series ofexo-methylenebenzocycloalkanes with ring sizes 5–8 have been prepared, enriched with13C and also deuterated at the exocyclic position.13C chemical shifts are found to be influenced by the degree of planarity between the aromatic ring and the exocyclic methylene function.13C–13C couplings through one, two, and three bonds have been measured. The1JCCvalues correlate very well with %Scharacter calculations. Values of3JCCare found to be influenced by both dihedral angle and valence angle. The relative propensity for these compounds to isomerize to endocyclic material is discussed. Some earlier spectral assignments for the indene derivative are shown to be in error.

ISSN:0008-4042    

DOI:10.1139/v79-493

出版商:NRC Research Press    

年代:1979

数据来源: NRC

摘要:

Reactions of various 5-aminopyrazoles with ethyl levulinate in acetic acid have been shown to furnish moderate to good yields of the correspondingly substituted 4-methyl-6H-pyrazolo-(3,4-b)azepin-7-ones, accompanied by the acetamidopyrazoles. The courses of methylation and of bromination reactions of some of the pyrazoloazepinones have been explored and defined, and conversion of one pyrazoloazepinone into 7-chloropyrazoloazepine and thence by nucleophilic displacements into 7-(substituted amino)pyrazoloazepines has been effected. Structural assignments, tautomeric preferences, and through-space interactions between substituents were established through nuclear magnetic resonance spectroscopy (1H and13C). Some members of the pyrazoloazepinone series exhibit significant anti-inflammatory and analgesic effects in mice.

ISSN:0008-4042    

DOI:10.1139/v79-494

出版商:NRC Research Press    

年代:1979

数据来源: NRC

摘要:

Second order rate constants for the oxidation by ozone of several acyclic acetals of heptaldehyde were determined at several temperatures. An isokinetic relationship is shown to exist for this series of reactions and the isokinetic temperature was found to be below the experimental temperature range, a domain of temperatures where reactivity is dominated by entropy factors. These results are contrasted with those obtained for cyclic acetals of heptaldehyde, where the isokinetic temperature falls above the working temperatures, a domain of temperatures where reactivity depends mainly on enthalpy factors. These results are interpreted in terms of a conformational change before oxidation in the acyclic acetals.

ISSN:0008-4042    

DOI:10.1139/v79-495

出版商:NRC Research Press    

年代:1979

数据来源: NRC

摘要:

Kinetics of reduction ofp-nitrotoluene by hydrazine in presence of Raney nickel catalyst have been studied spectrophotometrically. It has been found that the reaction is first order with respect to both hydrazine and nitrotoluene. The influence of solvent, salt, and the amount of catalyst on the reaction rate has been investigated. The rate constant was found to depend on the dielectric constant, the ionic strength, and on the catalyst concentration. The activation energy was estimated to be 103.92 kJ mol−1in 73.58% ethanol in water. This value decreases considerably when the polarity of the solvent increases and when other salts are added. In pure water the value is 32.25 kJ mol−1.

ISSN:0008-4042    

DOI:10.1139/v79-496

出版商:NRC Research Press    

年代:1979

数据来源: NRC

摘要:

The dissociation of pentafluoroacetone by high power infrared radiation fields is shown to proceed by a free radical mechanism.

ISSN:0008-4042    

DOI:10.1139/v79-497

出版商:NRC Research Press    

年代:1979

数据来源: NRC

摘要:

Molar heat capacities of crystalline pyrazine have been measured by adiabatic calorimetry in the range 20–40 °C and interpreted to show that in the crystal structures of phases II and III half the molecules must be disordered. Together with previous X-ray studies, this allows possible structures for phase II and phase III to be deduced. Of the eight molecules in the phase III unit cell, four are disordered over two sites so that the point symmetry is effectivelymmm; the remaining four molecules have 2/msymmetry and are not disordered. This structure is consistent with the available spectroscopic evidence. It is likely that the phase II structure is closely related to the phase III structure, for example by the molecules with 2/msymmetry adopting a slightly different orientation.

ISSN:0008-4042    

DOI:10.1139/v79-498

出版商:NRC Research Press    

年代:1979

数据来源: NRC

摘要:

Ni[Ag(SCN)2]2•2diox and its derivatives have been synthesized. Their structures have been given on the basis of infrared spectral, electronic spectral, magnetic moment, and molar conductance studies. These results demonstrate that Ni[Ag(SCN)2]2forms two types of complexes: (i) cationic–anionic type of general formula [NiLx]2+[Ag(SCN)2]22−(x = 3, 4, 6) and (ii) polymeric bridged type having a chain structure consisting of zig-zag thiocyanate bridges between nickel and silver. The cationic–anionic type of complexes are formed by pyridine, nicotinamide, 4-aminopyridine, aniline,p-toluidine, thiourea, ethylene thiourea, bipyridine, phenanthroline, pyrazine-2,3-dicarboxamide, and triphenylphosphine, and the polymeric bridged type by dioxane, acetone, and dimethylformamide. All the ligands have been found to prefer to coordinate to nickel instead of silver.

ISSN:0008-4042    

DOI:10.1139/v79-499

出版商:NRC Research Press    

年代:1979

数据来源: NRC