Sulphines. Part III. Kinetics of oxidation of thiobenzophenones with peroxybenzoic acid

Abstract

The oxidation of thiobenzophenones with peroxybenzoic acid is a two-step reaction, leading first to sulphines and then to the corresponding benzophenones. The first stage of the reaction is much faster than the second, so that the latter does not interfere with the kinetics of the former. A kinetic study of the first stage was carried out. The second-order rate constants measured at 25° in carbon tetrachloride for a series of thiobenzophenones fit the Hammett equation giving ρ=–0·88. The reaction rates of thiobenzophenone measured in carbon tetrachloride, methylene chloride, 1,4-dioxan, and ethanol correlate with the data reported for the oxidation of a sulphide and an olefin with the same peracid in the same solvent series. The results suggest that the relevant details of the mechanism of the reaction investigated here, are similar to those of the oxidation of sulphides to sulphoxides.