甲醇溶剂环境下两种稳定构象α-丙氨酸分子的手性转变机理  

The Chiral Transition Mechanism of Two Stable Conformations of α-Alanine Molecules in Methanol Solvent Environment

作　　者：方巍 丁蕾 杨庄 朱晓玉 孙建业 王佐成[3] 

机构地区：[1]白城师范学院化学学院,白城137000 [2]白城师范学院经济管理学院,白城137000 [3]白城师范学院物理学院,白城137000

出　　处：《复旦学报（自然科学版）》2017年第5期636-644,共9页Journal of Fudan University：Natural Science

基　　金：吉林省科技发展计划自然科学基金(20130101308JC);吉林省高等学校大学生创新项目(2017第116号)

摘　　要：采用密度泛函理论的B3LYP方法、微扰理论的MP2方法和自洽反应场(SCRF)理论的smd模型方法,研究了标题反应.势能面计算表明:标题反应的决速步骤均为第2基元反应,决速步能垒来自于质子从手性碳向氨基氮转移的过渡态.甲醇溶剂环境下构象1和2手性转变决速步的吉布斯自由能垒分别为109.8 kJ·mol^(-1)和111.0 kJ·mol^(-1),比气相甲醇环境下的决速步能垒134.2 kJ·mol^(-1)和130.8 kJ·mol^(-1)均有明显降低,比水环境下的决速步能垒122.5 kJ·mol^(-1)也明显降低,比裸环境下的决速步能垒266.1 kJ·mol^(-1)大幅降低,比限域在SWBNNT(5,5)内的决速步能垒为201.1 kJ·mol^(-1)也显著降低.结果表明:甲醇分子簇对α-丙氨酸分子的手性转变具有明显的催化作用,甲醇溶剂效应对质子从手性碳向氨基氮的转移反应具有较好的助催化作用.The chiral conversion mechanism of two kinds of the most stable configurations of α-alanine molecule in methanol solvation were researched by using the B3 LYP method of density functional theory,the MP2 method of perturbation theory,and smd model method of self consistent reaction field theory. Calculations of potential energy surface show that the second elementary reaction is step-determining in the title reaction. The step-determining Gibbs free energy barriers are 109. 8 kJ·mol^-1and 111. 0 kJ·mol^-1,respectively,which are generated by the transition state of proton transfer from the chiral carbon to the amino N,they are 134. 2 kJ·mol^-1and 130. 8 kJ·mol^-1in gaseous methanol.The step-determining Gibbs free energy barrier is 122. 5 kJ · mol^-1in water and is 266. 1 kJ · mol^-1in the isolation condition and is 201. 1 kJ·mol^-1in the SWBNNT（ 5,5）. It shows that methanol clusters have obvious catalytic effect on the chiral transition of α-alanine molecules and the methanol solvent has a better catalytic effect on the proton transfer from chiral carbon to amino nitrogen.

关 键 词：甲醇 手性转变 α-Ala 密度泛函理论 微扰理论 自洽反应场 过渡态 

分 类 号：O641.12[理学—物理化学]