The mechanism of hydrogen peroxide-induced aerobic oxidation of alkanes incatalysis by a vanadium complex and pyrazine-2-carboxylic acid

The vanadate anion catalyzes effective oxygenation of alkanes by air oxygen in acetonitrile in the presence of pyrazine-2-carboxylic acid (PCA) and hy drogen peroxide. The primary reaction product is an alkyl-hydroperoxide, wh ich gradually decomposes to the corresponding ketone (aldehyde) and alcohol . Activation of alkanes with respect to oxygen is caused by the attack of h ydroxyl radicals on alkane C-H bonds with the formation of alkyl radicals. Hydrooxyl radicals appear in the system as a result of interaction between a complex of a vanadium oxo derivative with PCA and hydrogen peroxide. The rate-determining step is the decomposition of the vanadium monoperoxo compl ex with PCA to a V(TV) derivative and hydroperoxyl radicals. The suggested kinetic model of the process satisfactorily describes the totality of the e xperimental data. The constants of supposed equilibria and the rate constan t for the decomposition of vanadium monoperoxo complex with PCA were estima ted.