The reactions of t-butyl peroxide with toluene derivatives, containing chloro-, bromo-, cyano-, methyl-, and phenylsubstituents in the alkyl side chain andp-halogeno-substituents in the nucleus, givevariable yields of the corresponding dehydro-dimers. Good yields are obtained with the p-halogeno-substituted cumenes, benzyl cyanide, p-chlorobenzyl cyanide, benzylidene dichloride, and p-bromoethylbenzene. a-Chloroethylbenzene, benzyl bromide, benzyl chloride, p-chlorobenzyl chloride, and p-tolunitrile give moderate to low yields of the expected dimers. However, p-bromobenzyl bromide, a-bromoethylbenzene, a-bromophenylacetonitrile, and diphenylbromomethane fail to dimerise in the expected manner. The available evidence in the case of diphenylchloromethane suggests that both hydrogen and chlorine are abstracted, giving rise to a variety of mixed products.FREE methyl radicals, liberated by thermolysis of acetyl peroxide, have long been known to abstract hydrogen atoms from the carbon atom adjacent to the unsaturated group in substances such as alkylbenzenes, ketones, acids, and esters1 More recently, similar behaviour has also been observed with t-butyl peroxide in its reactions with compounds containing the ArCH : nu~leus.~-4 This selectivity has been attributed to the effectiveness with which the t-butyloxy-radical can function as a dehydrogenating agent, when it is released from the thermal decomposition of t-butyl peroxide in a solvent. It has been established3'4 that the course followed by these homolytic reactions with t-butyl peroxide is largely determined by the relative stability of the secondary radical produced by hydrogen abstraction, provided polar-orienting and steric effects
