Topological aspects of odd graphs and their relevance to radical spin densities

Abstract

It is shown that all the α-electrons in π-electron free radicals are perturbed, which contrasts with previous recommendations. New expressions are derived for atom-atom and atom-bond polarisability coefficients in order to incorporate the perturbation of the odd α-electron.

In some alternant and non-alternant free radicals the error in electron placement is obscured by the identity between the unperturbed and perturbed molecular orbitals in which the odd α-electron is placed. Attention is drawn to correlations of this behaviour with certain topological properties of the graphs depicted by the free radicals.