Azines. A theoretical study of .pi.-electron delocalization

{pi}-electron delocalization in benzene and the azines has been studied theoretically in several ways: via an analysis of the first {pi} {yields} {pi}* transitions, via calculation of hydrogenation energies, and via an analysis of the wave functions. The electronic transitions suggest that the delocalization energies are essentially the same for all the compounds. The calculated energies for the addition of 1 equiv of hydrogen suggest that the resonance energies of benzene, pyridine, pyrazine, and pyrimidine are essentially the same. The values for the other azines appear to be smaller, but this may in part arise from changes in the {sigma}-systems. The distribution of {pi}-electron density around the rings does not appear to be strongly perturbed by the replacement of CH by N.