The Bond Orbital Approximation for π-electron System in Benzene

Abstract

The electronic energies of π-electron system in benzene molecule have been calculated by the bond orbital (BO) method for singlet states. Configuration interactions (CI) have not been taken into account. All the levels other than ¹B_2u and ¹E_2g calculated by the present method are higher than the levels calculated by the MO method without CI. In the MO method, however, the order of levels is changed and coincides with the observed order, by including CI. In the BO method the order of levels would not be changed by including CI, since the BO method without CI already gives the correct order.