Kinetics of the metathetical reaction between carbon tetrachloride and toluene

A metathetical reaction between carbon tetrachloride and toluene to give benzyl chloride and chloroform occurs at temperatures above 200°C (k = 4.8 × 1010 e−32,900/RT cc mole−1sec−1). The reaction does not involve free radicals, as is shown by the kinetic behavior of the system, by the lack of effect of added free-radical chain inhibitors, and by the absence of the expected chain termination product, hexachloroethane. The reaction is one of a general type between carbon tetrachloride and alkanes or alkylaromatics, but at the temperatures required it is often obscured by dehydrohalogenation of the product to the highly reactive olefin. At high temperatures, benzyl chloride reacts with toluene to give bibenzyl and hydrogen chloride, apparently also by a metathetical reaction. The transition state is postulated to be four-center, in which the carbon-chlorine and carbon–hydrogen bonds are broken and reformed: The experimental preexponential factor is in good agreement with that calculated from transition-state theory.