The electronic structure of dialkylbenzenes

Abstract

A new CNDO model parametrization, differing from earlier ones primarily by its embodiment of large orbital exponents for conjugated carbon atoms, is proposed for the description of the electronic spectra of aromatic hydrocarbons. In contrast to its predecessors, the new model is shown to describe both the ultraviolet absorption and the valence electron eigenvalue spectra of methyl substituted benzenes. The predictions of this model are compared with those of earlier molecular‐orbital calculations (Hartree–Fock, CNDO/2, and SPINDO) and with the ultraviolet‐photoemission and ultraviolet‐absorption spectra of benzene, p‐xylene, m‐xylene, and 1,4‐bis(trifluoromethyl) benzene. The model also correctly predicts the symmetry of the radical anion ESR spectra of those compounds for which they have been measured.