The kinetics and mechanism of the hydrolysis of thiol esters in aqueous solution promoted by tetrachlorogold(III) ions

Abstract

The hydrolysis of S-ethyl p-methoxy- and of S-ethyl p-nitro-thiobenzoate is promoted by tetrachlorogold(III) and related ions. The hydrogen ion-catalysed hydrolysis is very slow by comparison. Kinetic studies show that in the promoted reactions, at suitable ambient chloride concentrations, simultaneous promotion by AuCl₄^–, AuCl₃(OH)^–, and AuCl₃(H₂O) is involved. Substituent effects, activation parameters, solvent isotope effects, and the absence of a common ion effect at high chloride ion concentrations all combine to suggest that the reaction mechanism involves slow metal transfer to sulphur.