Kinetics of inhibited or retarded polymerization. Investigations on the cerium(IV)/toluene/acrylonitrile system

The kinetics and mechanism of the inhibiting action of toluene on the Ce(IV) initiated polymerization of acrylonitrile were studied together with the effects of M], Ce(IV)], Toluene], HClO₄], NaClO₄], and Acetic acid] on the rate of polymerization. The values of composite rate constant kk_t/k_pk_ok_i for toluene (and substituted toluenes) was calculated by plotting M]/R_p versus M]^?1. A very significant observation in the present study was that the plot of M]/R_p versus M]^?1 gave a negative intercept, which seems to be a general observation for all inhibiting substrates. On the basis of the experimental data, it could be concluded that the benzyl radical obtained by hydrogen abstraction, and not a chain transfer, is responsible for the inhibition.