The kinetics during the early stages of the photochemically initiated radical chain chlorinations of toluene, p-xylene, t-butylbenzene, triphenylmethane, cyclohexane, and chloroform with t-butyl hypochlorite have been studied at 24°. With the exception of chloroform, the kinetics are consistent with chain termination by the combination of t-butoxy radicals and hydrogen atom abstraction by these radicals as the rate-determining propagation step. The absolute rate constants for the rate-determining steps in the chlorination of the above substrates have been measured. The rate constant for the combination of t-butoxy radicals in solution (2k6) is about 2 × 108 M-1 sec-1. The rate constant for hydrogen abstraction from toluene by t-butoxy radicals is given by k2 = 6.7 × 107 exp(-5600/RT) M-1 sec-1.
Journal of the American Chemical Society89, no. 19 (1967): 4891–4894.