Mechanism of antioxidant action: reactions of alkyl and aryl sulphides with hydroperoxides

Abstract

The aryl sulphides 3,3′,5,5′-tetra-t-butyl-4,4′-dihydroxydiphenyl sulphide (1), the corresponding disulphide (2), trisulphide (3), and tetrasulphide (4), and the alkyl sulphides di-t-butyl sulphide (7) and dibenzyl disulphide (10) have been used to catalyse the decomposition of 1-methyl-1-phenylethyl hydroperoxide (cumene hydroperoxide) at 393 K. The decompositions are catalytic pseudo-first-order reactions. The kinetic data and product studies demonstrate that the catalyst for hydroperoxide decomposition is sulphur dioxide. The mechanism for formation of the sulphur dioxide has been demonstrated to involve oxidation of the sulphides and decomposition of the resulting thermally unstable sulphur–oxygen compounds. The results demonstrate that the thermal chemistry of sulphur–oxygen compounds (sulphoxides, thiolsulphinates, etc.) formed from the sulphides determines whether or not the sulphide will catalyse hydroperoxide decomposition.