Oxidations by the reagent «O 2 - H 2O 2 - vanadium complex - pyrazine-2-carboxylic acidå-8 : Efficient oxygenation of methane and other lower alkanes in acetonitrile

Abstract

Methane, ethane, propane, n-butane and isobutane can be readily oxidized in acetonitrile solution by air and H 2O 2 at 20–75 °C using the catalytic system [ n-Bu 4N]VO 3/pyrazine-2-carboxylic acid. Apart from alkyl hydroperoxides which are the primary oxidation products, more stable derivatives (alcohols, aldehydes or ketones and carboxylic acids) are obtained with high total turnover numbers (e.g., at 75 °C after 4 h: 420 for methane and 2130 for ethane). It was shown in the case of ethane and cyclohexane that alkanes do not yield oxygenated products in the absence of air. The cyclohexane oxidation under an 18O 2 atmosphere showed a high degree of 18O incorporation into the oxygenated products. Thus in the oxidation reaction described here H 2O 2 is only the promoter while O 2 is the “true” oxidant.