用密度泛函论分析X-CH_2-CH_2-X(X=H,CH_3,OH,NH_2,SH,F,Cl,Br,I)的构象

Conformational analysis of X-CH_2-CH_2-X(X=H,CH_3,OH,NH_2,SH,F,Cl,Br,I) by density functional theory

为了研究X-CH_2-CH_2-X(X=H,CH_3,OH,NH_2,SH,F,Cl,Br)的构象,采用密度泛函理论的量子化学计算方法,扫描其势能而,分析其典型构象,——得出稳定构象,并分析了最影响其稳定构象的原因。结果表明,对于正丁烷、1,2-二氯乙烷、1,2-二溴乙烷和乙二巯醇,对位交叉构象最稳定,影响其最稳定构象的主要因素是空间作用:对于乙二醇,乙二胺,邻位交叉式为其最稳定的构象,该构象稳定的主要因素是分子内氢键;偶极-偶极相互作用导致1,2-二氟乙烷的最稳定构象是邻位交叉式;超共轭作用导致乙烷的最稳定构象为对位交叉。用理论化学计算,可以确定分子的最稳定构象,应从多方面分析影响分子最稳定构象的原因。

In order to determine the conformations of X-CH2-CH2-X（X=H, CH3, OH, NH2, SH, F, Cl, Br）, the potential energy surfaces were scanned and the typical conformations were analyzed by Density Functional Theory. The most stable structure of each molecule was obtained and the reasons for the most stable conformation of them were analyzed. The results showed that steric hindrance effect results in the most stable staggered conformation of n-butane, 1,2-dichloroethane, 1,2-dibromoethane and SH-CH2-CH2-SH, the most stable conformation of glycol and 1,2-ethylenediamine is gauche form, as a result of the effect of intramolecular hydrogen bond, the most stable conformation of F-CH2-CH2-F is gauche form, owing to the dipole-dipole interaction.The most stable conformation of the molecules can be computed by quantum chemistry. The reasons of the stability should be explained from different points.