OXIDATION OF SUBSTITUTED S-PHENYLMERCAPTOACETIC ACIDS BY QUINOXALINIUM DICHROMATE

摘要

The conversion of S-phenylmercaptoacetic acid to the corresponding sulphoxide was performed in 50% (v/v) water-acetic acid mixture in the presence of perchloric acid medium. The order with respect to S-phenylmercaptoacetic acid and quinoxa-linium dichromate were both one and inverse first order with respect to hydrogen ion concentration. Decrease in dielectric constant of the medium increased the rate of reaction. Ionic strength had a considerable influence on a reaction rate, indicating the involvement of a dipole in the rate-limiting step. In general, the electron-withdrawing substituents enhance the reaction rate and electron-releasing substituents retard the reaction rate. A suitable mechanism and rate law in consonance with the observed facts is proposed.