The reaction of methyl radicals with hydrogen peroxide

Abstract

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 + H₂O₂) = 2.7 × 10⁴ dm³ mol^–1 s^–1. As the corresponding rate constant in the gas phase is reported to be 3.3 × 10⁷ dm³ 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.