DOUBLE-BOND FIXATION IN CONJUGATED PI-ELECTRON SYSTEMS .V. SELF-CONSISTENT FIELD CALCULATIONS FOR NONALTERNANT HYDROCARBONS AND NITROGEN HETEROCYCLES

The SCF theory of first-order and second-order double-bond fixation of the preceding paper is applied to a variety of nonalternant hydrocarbons, benzo derivatives of cyclobutadiene, and aza analogs of alternant and nonalternant π-electron systems. It is found that second-order bond distortions play a dominant role in certain systems that have previously been classified as pseudoaromatic. A new aromaticity criterion is proposed which is entirely based on double-bond fixation. The theoretical conclusions are found to be in gratifying agreement with chemical experience in those cases where experimental information is available. © 1969, American Chemical Society. All rights reserved.