The nature of the inductive effect of azinyl groups

The induction constants of azinyl groups are factored into two components, a sigma-induction (sigma/sub X/) and a field (sigma/sub F/) component. It is shown that the sigma/sub X/ constants of azinyl groups can be thought of as sums of contributions from the phenyl group and the endocyclic nitrogen atoms. A satisfactory correlation is found between the sigma/sub F/ constants and the size and direction of the dipole moment of the heterocyclic substituents in the framework of the Kirkwood-Westheimer equation.