Influence of substituent groups in the arylation of substituted benzenes by aryl radicals derived from p-substituted N-nitrosoacetanilides

Abstract

The partial rate factors for the homolytic arylation of substituted benzenes by substituted phenylradicals generated from p-substituted N-nitrosoacetanilides are presented, and the influence of a substituent is shown to be divided into two parts which are attributable to the inductive and the conjugative effect respectively. Hammett's relations hold for the partial rate factors for the arylations at the meta position. The correlation of the ϱ values with the inductive constants for the substituent groups in the arylating radicals indicates that the effect of a substituent in the radical is purely inductive in nature. The partial rate factors for arylations at the position para to a substituent in benzene are related to Hammett's substituent constant σ p by the equation: log (k p/k) = ϱσ p + τ p, where τ is a constant dependent on the nature of the substituent in the substrate and represents its conjugative capacity. On the assumption that the corresponding relation holds for the ortho position as well, very reasonable values of σ 0 and τ 0 are derived from the k 0/k and ϱ values.