乙醛二聚体的从头计算

AB INITIO MOLECULAR ORBITAL ON THE ACETALDEHYDE DIMER

用a6 initio分子轨道法在STO-3G和6-31G水平上,全构型优化,对二聚乙醛的各种稳定构型进行了研究。结果表明,在STO/6-31G水平上,最稳定的乙醛二聚体为具有对称中心的环状结构,包含由醛基氢和醛基氧组成的二个C—H…O氢键。结合能为-20.17kJ·mol^(-1),与实验估计的结合能-22.39±0.15kJ·mol^(-1)比较接近。STO-3G过低估计了乙醛二聚体的结合能,在不同构型的相对稳定性方面也与6-31G不一致。

Ab initio molecular orbital calculations were performed on various structures of the acetaldehyde dimer at STO-3G and 6-31G levels. All the fully optimized structures of the dimer are cyclic structures with two C—H…O hydrogen bonds. At 6-31G level, the most stable geometry of the dimer is a symmetric one and the C—H…O hydrogen bonds are composed of hydrogen in—CHO group and carbonyl oxygen. The binding energy is —20.17 kJ. mol^(-1), which is in reasonable agreement with the estimated experimental value of -22.39±=0.15 kJ. mol^(-1). The STO-3G basis set underestimates the binding energy and fails to give consistent description of the relative stabilities of various structures of the dimer with the 6-31G basis set.