Kinetics of the reaction between thioglycolic acid and parabenzoquinone-Micellar effect of cetyltrimethyl ammonium bromide

Abstract

Parabenzoquinone (PBQ) undergoes 1-4 addition reaction with thioglycolic acid (TGA) forming parabenzoquinone monothioglycolic acid when the quinone is present in excess. To

understand the mechanism of the reaction a detailed kinetic study of the reaction has been undertaken. The reaction obeys first order kinetics with respect to PBQ and TGA, but is inhibited by H⁺ ion. A plot of the reciprocal of the pseudo-first order rate constant vs [H⁺] is linear with a positive slope and intercept. The reaction is markedly accelerated by the positively charged cetyl trimethyl ammoniumbromide micelles. The rate-[surfactant] profile shows a limiting behaviour indicative of unimolecular rate-determining reaction in the micellar pseudo-phase.