中文摘要：

基于密度泛函理论,对孤立条件下的α-丙氨酸分子手性转变过程和水分子对此过程中氢转移的催化作用进行了研究.通过寻找过渡态和中间体等极值点的结构,绘制了孤立条件下α-丙氨酸分子手性转变的过程以及水环境中重要氢转移过程的势能面.结果表明,孤立条件下α-丙氨酸分子手性转变有2条路径：路径1由3个中间体和4个过渡态组成,最高能垒337.4kJ·mol^-1来自羧基的氢向甲基迁移和甲基的氢向手性碳迁移的协同过程.路径2由4个中间体和5个过渡态组成,最高能垒316.3kJ·mol^-1来自手性碳上的氢向羧基上氧的转移.单个水分子和2个水分子作为氢转移的桥梁,使路径2的最高能垒从316.3kJ·mol^-1分别降到198.0和167.8kJ·mol^-1.

英文摘要：

Based on the density functional theory（DFT）,the chiral transformation ofα-alanine molecules and the catalysis of water molecules to hydrogen transfer have been studied under isolated conditions in this paper.By searching for the extreme point structure of transition states and intermediates,the potential energy surfaces ofα-alanine molecule chiral transition process under isolated conditions as well as two important hydrogen transfer processes in the water environment are drawn.The results show that under the isolated conditions,there are two paths for the chiral transformation ofα-alanine molecules.Path 1consists of three intermediates and four transition states.The maximum energy barrier of hydrogen is 337.4kJ·mol-1 resulting from the collaborative process that hydrogen on carboxyl transfers to methyl,as well as the hydrogen on methyl transfers to chiral carbon.Path 2consists of four intermediates and five transition states.The maximum barrier of hydrogen is 316.3kJ·mol^-1 resulting from the process of the hydrogen on chiral carbon to oxygen on carboxyl.The maximum barriers in path two are reduced from316.3kJ·mol^-1to 198.0kJ·mol^-1 and 167.8kJ·mol^-1 respectively when one or two water molecules act as the hydrogen transfer bridge.