Substituent parameters for radical reactions Cerium(IV) — substituted toluenes — acrylonitrile system

Summary

In the present study, a new approach for the determination of σ', that is, radical substituent parameter, has been described. The technique is based on two equations, one reported byYamamoto andOtsu and the other byStreitwieser andPerrin. The system used for the determination of the radical substituent parameter (σ') was Ce(IV) — substituted toluenes — acrylonitrile system. To explain inhibition, it has been suggested that the reaction scheme involves initiation of polymerization by Ce(IV) and termination by primary radical of the substrate. The kinetic expression based on the reaction scheme formulated could explain the unusual observation of a negative intercept found in the plot of [M]/R _p versus 1/[M]. Whereas a plot of log κ/κ₀ against σ⁺ did not give a straight line, a good linear plot with zero intercept was obtained when log κ/κ₀ was plotted against (σ⁺ + σ'). This proves the validity of σ' values which have been determinded.