Reactivities of Chlorine Atoms and Peroxyl Radicals Formed in the Radiolysis of Dichloromethane

Article abstract of DOI:10.1021/j100341a040

Radiolysis of dichloromethane (DCM) leads to formation of primary oxidizing radicals and carbon-centered radicals.The latter react with oxygen to yield peroxyl radicals.The yields and chemical behavior of these intermediates were studied by pulse radiolysis of DCM solutions containing various solutes: phenols, anilines, dimethoxybenzene, hexamethylbenzene,cyclohexene, dimethyl sulfoxide, and zinc tetratolylporphyrin.At low concentrations, some of these solutes were found to be oxidized by two peroxyl radicals, CH2ClO2* and CHCl2O2*, with different rate constants.At higher concentrations, the solutes react also with the primary radicals: Cl atoms and the radical cations CH2Cl2(+*), with diffusion-controlled rate constants.The rates of these reactions were determined by competition kinetics because of the very short lifetimes of the species.Cl atoms were found to have a half-life of about 5 ns in DCM, reacting predominantly with the solvent by hydrogen abstraction.The radical cations decay within a fraction of a nanosecond.The total yield of these primary radicals was determined to be G = 3.6 and appears to be divided about equally between Cl and the radical cations.The total yield of oxidation, by the primary and the peroxyl radicals, was found to be G = 7.5.Cl atoms were found to be very reactive in electron transfer as well as addition and hydrogen abstraction reactions.