The oxygen exchange between sulphoxides and sulphides. The hydrogen chloride catalysed reaction between p-chlorophenyl methyl sulphoxide and dibutyl sulphide

Abstract

Alkyl aryl sulphoxides are reduced by dialkyl sulphides in 2 : 1 methanol–water in the presence of 4M-HCl. The kinetics of the reaction between p-chlorophenyl methyl sulphoxide and dibutyl sulphide and the basic properties of the sulphoxide have been investigated in detail. Reaction orders, acid catalysis, and comparison of the reduction rate with that of the loss of optical activity by the (+)-R-sulphoxide indicate a predominant role for the chlorosulphonium cation. A mechanism is suggested in which the changes of the oxidation states occur through the reaction between the sulphide and this intermediate.