Metal catalysis in oxidation by peroxides. Vanadium catalysed oxidation of organosulphur compounds by t-butyl hydroperoxide

Abstract

The reaction of di-n-butyl sulphide with t-butyl hydroperoxide proceeds at a convenient rate in ethanol at 25° in the presence of catalytic amounts of bisacetylacetonato-oxovanadium(IV)[VO(acac)₂] affording di-n-butyl sulphoxide in quantitative yield. With [Bu^tO₂H]₀/[VO(acac)₂]₀ 8 and [VO(acac)₂]₀ 0·0001–ca. 0·002M the reaction is first order in sulphide and first order in vanadium catalyst. With an excess of sulphide and varying the initial concentration of hydroperoxide, the kinetics conform to a Michaelis–Menten-type rate law. The relative rates of vanadium catalysed oxidation of some substrates by Bu^tO₂H were found to decrease in the order Buⁿ₂S (100) > PhSBuⁿ(58) > Buⁿ₂SO (1.7) > cyclohexene (0·2). The data suggest a mechanism involving rate-determining nucleophilic attack by the sulphur substrate on the O–O bond of a hydroperoxide–vanadium(V) complex.