The reactions of methyl radicals with chloromethanes

Abstract

AbstractThe reaction of methyl radicals with CCl4 and CCl3Br have been reinvestigated in the gas phase over a wide range of temperatures and pressures using both the photolysis of acetone and the pyrolysis of di‐tertiary butyl peroxide (dtBP) as the methyl radical sources. The results are in essential agreement with previous work; however, these new studies provide evidence that at higher pressures the major source of HCl in the reactions is due to methyl radical attack on CH3CCl3, formed via the combination of methyl and trichloromethyl radicals.From these investigations Arrhenius parameters for the reactions equation image have been determined: Pyrolysis of dtBP in the presence of relatively high‐pressure mixtures of CCl4 and CCl3Br resulted in no enhanced methane formation, since, under these conditions, the only termination product is C2Cl6, and the HCl precursor CH3CCl3 is not formed. A competitive technique has been used in which dtBP was pyrolysed in the gas phase in the presence of high‐pressure mixtures of CCl3Br and a chloromethane. Arrhenius parameters were obtained for the reactions equation image and the results were used to provide information on the importance of polar effects for hydrogen abstraction from halogenated methanes.