Oxidation of saturated hydrocarbons with peroxyacetic acid catalyzed by vanadium complexes

Peroxyacetic acid (PAA) oxidizes alkanes in acetonitrile or acetic acid at 60degreesC if a soluble vanadium(V) salt, n-Bu4NVO3 (1), is used as a catalyst. Corresponding ketones, alcohols and alkyl hydroperoxides are the main products. Methane, ethane, propane, cyclohexane, and other higher alkanes were substrates in the oxidations. The proposed mechanism involves the formation of a complex between (1) and PAA with equilibrium constants 3.3 and 6.8 dm(3) mol(-1) for acetonitrile and acetic acid as solvents, respectively. This complex decomposes to produce CH3C(=O)OO. radical and a V-IV derivative. The latter reacts with PAA to generate a CH3C(=O)O-. radical which attacks the alkane abstracting its hydrogen atom. An alkyl radical thus formed adds rapidly a molecule of dioxygen which leads finally to the alkyl hydroperoxide and then to the ketone and alcohol. Other vanadium(V) and vanadium(IV) complexes are also active in this oxidation only if the vanadium ion is not shielded with strongly bound bulky ligands. (C) 2004 Elsevier B.V. All rights reserved.