Sulfide oxidation and oxidative hydrolysis of thioesters by peroxymonosulfate ion

Abstract

Peroxymonosulfate ion, HSO₅^–, as OXONE, in aqueous MeCN readily converts aryl thiobenzoates, XC₆H₄CO·SC₆H₄Z (X =p-OMe, p-Me, H, p-Cl, p-CN; Z=p-OMe, p-Me, H, m-OMe, p-Cl, m-Cl, p-NO₂) into carboxylic and sulfonic acids. Reactions are second order and have small substituent effects, with p≈–0.6 based on σ_m and σ_p substituent parameters, but rates increase markedly with increasing water content in aqueous MeCN and entropies of activation are negative. The initial step is very similar to the oxidation of methyl aryl sulfides by HSO₅^– which has similar solvent and substituent effects. Enthalpies of activation are much lower for oxidation of the sulfides than of the corresponding esters but entropies of activation are similar.