The kinetics have been determined for the photochemically initiated (24°) and thermally initiated (30°) radical chain chlorination of toluene in CCl4 by t-butyl hypochlorite. In the initial stages of the reaction the rate is approximately proportional to the first power of the toluene concentration and to the square root of the rate of initiation. These kinetics apply over a wide range of relative and absolute toluene and hypochlorite concentrations. They imply that hydrogen atom abstraction from the toluene by t-butoxy radicals is the rate-controlling step of chain propagation and that chain termination involves the mutual destruction of two t-butoxy radicals. At high conversions the reaction is strongly autoaccelerating, and the kinetics become more complex. It is suggested that the autoacceleration is due to the formation of an unstable intermediate which can break down and initiate new reaction chains.
Date de publication
Journal of the American Chemical Society89, nº 19 (1967) : 4885–4891.