Elucidation on the Treatment of <i>π</i> Bond Orders of Naphthalene with H&#252;ckel Molecular Orbital Method

Abstract

Generally, the bigger π bond order of conjugated olefins is corresponding to the shorter bond length. However, some π bond orders of naphthalene calculated by the Hückel molecular orbitals (HMO) method do not match the experimentally measured bond lengths, thus many students questioned the accuracy of the computed results using the HMO method. In this work, we employed ab initio Hartree-Fock (HF) method and suggested a revised HMO method with correction factor to recalculate and provide more reasonable π bond orders of naphthalene. By comparing the results calculated by the semi-empirical HMO and HF methods, this article can make the students understand origin of the computational error by using HMO method.