Oxidation of S-phenylmercaptoacetic acid by quinoxalinium dichromate

The conversion of S-phenylmercaptoacetic acid to the corresponding sulfoxide was performed in 50% (v/v) wateraceticacid mixture in the presence of perchloric acid medium. The order with respect to S-phenylmercaptoacetic acid and quinoxalinium 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. A suitable mechanism and rate law in consonance with the observed facts is proposed

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