Molecular orbital perturbation theory II. Charge displacement and stabilization in conjugated molecules

The general perturbation method outlined in part I is used to study energy and charge distribution changes caused by inductive and electromeric-type perturbations in conjugated molecules. Self-consistent orbitals for the unperturbed systems are found by approximating electron interaction integrals and are used as a basis for the perturbed systems. It is found that the change of charge distribution caused by an inductive substituent in benzene is similar to that predicted by the independent-electron model. Second-order perturbation theory is used to discuss electromeric displacements in which lone pair electrons take part in conjugation.