ISSN:
0894-3230
Keywords:
carboxylic acids
;
Crystal Violet carbinol base
;
apolar aprotic solvents
;
benzoic acids
;
toluene
;
Chemistry
;
Theoretical, Physical and Computational Chemistry
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
,
Physics
Notes:
---Equilibria and kinetics of proton-transfer reactions in toluene between a set of m- and o-substituted (methyl, methoxy, chloro, nitro and hydroxy) benzoic acids and the carbinol base (colourless) of Crystal Violet were studied spectrophotometrically. The data on equilibrium and kinetic parameters were critically analysed. The rate constant for the forward step of the acid-carbinol equilibrium was found to be an appropriate criterion for determining acidities in toluene. Toluene-phase acidities were found to be significantly more susceptible than aqueous-phase acidities to the structure of the substituents, particularly for the m-substituted acids. Quantitative analysis of the substituent effect on toluene-phase acidities using the Fujita-Nishioka model for the extended Hammett equation showed that the predominant factor contributing to the "ortho effect" for benzoic acid-dye carbinol reactions in toluene is the proximity polar effect rather than the steric effect for most of the o-substituents. © 1997 John Wiley & Sons, Ltd.
Additional Material:
2 Ill.
Type of Medium:
Electronic Resource
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