休克尔分子轨道法处理萘的π键键级的释疑

Elucidation on the Treatment ofπBond Orders of Naphthalene with Hückel Molecular Orbital Method

一般来说,共轭体系的π键键级越大则其键长越短。然而,休克尔分子轨道(HMO)法计算出部分萘的π键键级与实验测得的键长数值并不相符,因此不少同学质疑HMO法计算的准确性。本文运用从头算Hartree-Fock(HF)方法和尝试加入校正因子的HMO法得到了更合理的萘等并环π键键级,并通过比较使学生进一步理解HMO法的误差来源。

Generally,the biggerπbond order of conjugated olefins is corresponding to the shorter bond length.However,someπbond 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 reasonableπbond 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.