The reaction of methyl radicals with hydrogen peroxide

Methyl radicals (plus methanesulfinic acid) were generated radiolytically in N2O-saturated aqueous solutions by reacting the OH radicals thus formed with dimethyl sulfoxide. Upon addition of hydrogen peroxide the methyl radicals abstract an H-atom from hydrogen peroxide. With increasing hydrogen peroxide concentrations the methane yield increases while that of ethane drops. The yield of methanesulfinic acid remains unaffected. At constant hydrogen peroxide concentration, the ethane yield increases with increasing dose rate. The system has been successfully modelled using k((CH3)-C-. + H2O2) = 2.7 x 10(4) dm(3) mol(-1) s(-1). As the corresponding rate constant in the gas phase is reported to be 3.3 x 10(7) dm(3) mol(-1) s(-1), the water solvent appears to have a dramatic effect. Some aspects of the mechanism of H-abstraction from H2O2 are briefly discussed.