Use of the CNDO Method in Spectroscopy. II. Five-Membered Rings

Abstract

The modified CNDO method previously reported has been used to calculate the electronic spectra of cyclopentadiene, the cyclopentadienide ion, pyrrole, furan, pyrazole, imidazole, 2-pyrrolecarboxaldehyde, and furfural. In general, the results obtained agree quite well with experimental data. Because the CNDO method treats explicitly all σ and π valence electrons of a molecule, the results of the calculations are used to discuss some of the σ–π interactions which previously could not be treated. The calculations are successful in reflecting changes in the electronic spectra of compounds as a result of extending conjugation or addition of a substituent.