Reactions of Methylene Radicals with Benzene and Toluene in the Gas Phase

Abstract

Abstract The reactions of methylene radicals produced by the photolysis of ketene with benzene and with toluene in the gas phase have been studied. The reaction of methylene with benzene gave cycloheptatriene and toluene in a ratio 7 to 3. The ratio varied neither with the pressure raised by the added nitrogen or carbon dioxide nor with the wave lengths of the incident radiation. The products obtained in the reaction of methylene with toluene were ethylbenzene, m-xylene, p-xylene and an unidentified product, their percentages being 25, 40, 25 and 10% respectively. About a five-fold increase in the amount of ethane has been observed over that observed in the reaction with benzene or in the photolysis of pure ketene. This fact indicates that the abstraction of the hydrogen atom by methylene from the methyl in toluene does occur, but that that from the benzene ring does not. Oxygen did not alter the relative yield among the products in the reactions of methylene with either benzene or with toluene. This suggests that the products are formed by the reactions of singlet methylene with benzene and toluene via norcaradiene-type intermediates. It has quantitatively been shown that the reactivity of methylene redicals is very high with aromatics, ethylene and acetylene, as with ketene.