两个典型SN2反应体系的电子定域函数拓扑特征研究

发布时间：2018-05-06 06:17

本文选题：电子定域函数 + 拓扑分析　；参考：《河北师范大学》2017年硕士论文

【摘要】：论文在B3LYP/6-31G*的计算水平上对两个典型的SN2反应体系Cl+CH_3Cl→ClCH_3+Cl和HO+CH_3Br→HOCH_3+Br反应中的各个驻点的构型进行了全优化,得到了各驻点的稳定几何结构,体系总能量和分子体系波函数;采用实验室自编的程序GTA对两个反应IRC过程中的各结构的电子密度拓扑性质和电子定域函数拓扑性质进行了计算;积分得到了各结构中各类电子定域函数拓扑分析得到的各Basin的电子数;对反应过程中电子密度拓扑指标和电子定域函数定义下的各Basin电子密度积分值的变化进行了讨论分析。揭示了两个典型SN2反应中化学键在生成和断裂的本质特征变化和定量化转化规律。在第一章中,主要是对SN2的反应类型做简单的介绍,对本论文研究使用到的电子密度拓扑分析基本概念和电子定域函数拓扑空间区域(Basin)分析做了简单的介绍。第二章主要是就该论文在研究过程中用到的理论化学知识和量子化学的计算方法做简单的描述。第三章中对Cl+CH_3Cl→ClCH_3+Cl的化学反应IRC过程和IRC过程中的各结构的电子密度拓扑性质和电子定域函数拓扑性质进行了计算,对得到的计算结果进行了分析和讨论。研究发现,对于SN2反应体系Cl+CH_3Cl→ClCH_3+Cl,C-Cl1键的断裂和C-Cl3键的形成是同时进行的;ELF拓扑分析得到的键域的特征分析能够给出反应过程中化学键变化的本质特征:C-Cl键鞍点电子密度变化和V(C-Cl)电子密度积分值变化分析显示,在过渡态形成之前,即将断裂的C-Cl键以共价键的形式存在,而逐步形成的C-Cl键以闭壳层相互作用的形式存在(不是典型的共价键),在过渡态形成之后亦然;ELF拓扑分析得到的各类域中电子密度积分值的变化可以定量地给出化学键变化的过程特征:反应过程中电子定域函数拓扑分析给出的各Basin中的电子密度积分值变化的分析显示,内层电子基本不参与和影响化学反应过程中的化学键形成和断裂,C-H键较小程度地参与了化学反应过程中的化学键变化,共价键C-Cl的断裂和生成与Cl孤对电子相互转移存在定量的关系V(C-H4)、V(C-H5)、V(C-H6)的数值都是随着V(C-Cl1)值的减小增加,随着V(C-Cl3)值的增加而减小;C和H之间的相互作用随着C-Cl1间化学键的断裂而增强,随着C-Cl3间键的逐渐形成而减弱,且在过渡态时C和H之间的相互作用最强;L(Cl-1)的数值随着V(C-Cl1)的值的减小而增加,同时L(Cl-3)的值也是随着V(C-Cl3)的增加而减小。第四章对SN2体系HO+CH_3Br→HOCH_3+Br的化学反应的电子定域函数拓扑分析进行了计算和分析讨论。结果显示,C-Br键的断裂和O-C键的形成是同时进行的,但根据HO+CH_3Br→HOCH_3+Br IRC过程中C-Br键域V(C-Br)和C-O键域V(C-O)电子密度积分值变化分析,在过渡态形成之前,即将断裂的C-Br键以共价键的形式存在,而逐步形成的O-C键以闭壳层相互作用的形式存在(不是典型的共价键);在过渡态形成之后,C-Br键以闭壳层相互作用的形式存在,而O-C键以共价键的形式存在;反应过程中电子定域函数拓扑分析给出的各类Basin中的电子密度积分值变化的分析显示:在HO+CH_3Br→HOCH_3+Br反应过程中,内层电子基本不参与和影响化学反应过程中的化学键形成和断裂,C-H和O-H键较小程度地参与了化学反应过程中的化学键变化,共价键C-Br的断裂和O-C的和生成与Br、O原子的孤对电子成分存在定量的电子相互转移。
[Abstract]:This paper optimizes the configuration of two typical SN2 reaction systems, Cl+CH_3Cl, ClCH_3+Cl and HO+CH_3Br to HOCH_3+Br at the level of B3LYP/6-31G*, and obtains the stable geometric structure of the stationary points, the total energy of the system and the wave function of the molecular system, and the two reaction IR with the program GTA compiled by the laboratory. The topological properties of the electronic density and the electronic domain function of each structure in the C process are calculated. The integral obtains the number of electrons of each Basin obtained by the topological analysis of various electronic domain functions in each structure, and the Basin electronic density integral values of the electron density topological index and the electronic domain function in the reaction process are defined. The changes are discussed and analyzed. The changes of essential characteristics and quantitative transformation of the chemical bonds in the two typical SN2 reactions are revealed. In the first chapter, a brief introduction to the type of SN2's reaction is made, and the basic concepts of the electronic density topology and the topological space of the electronic domain are discussed in this paper. The region (Basin) analysis is briefly introduced. The second chapter is mainly about the simple description of the theoretical and quantum chemical knowledge used in the research process and the calculation method of quantum chemistry. In the third chapter, the IRC process of the chemical reaction to the ClCH_3+Cl and the topological properties of the electron density of each node in the IRC process and the electron fixed domain function in the IRC process The number of topological properties is calculated and the results obtained are analyzed and discussed. It is found that the fracture of the C-Cl1 bond and the formation of the C-Cl3 bond are carried out at the same time for the SN2 reaction system Cl+CH_3Cl to ClCH_3+Cl; the characteristic analysis of the key domain obtained by the ELF topology analysis can give the essential characteristics of the chemical bond changes in the reaction process: C-Cl The change of the electron density of the keysaddle point and the change of the V (C-Cl) electron density integral value shows that before the transition state is formed, the broken C-Cl bonds exist in the form of covalent bonds, and the C-Cl bonds formed gradually in the form of the closure of the shell layer (not the typical covalent bond), after the transition state is formed, and the ELF topology analysis is obtained. The changes in the integral value of the electron density in various domains can give a quantitative analysis of the process characteristics of the chemical bond change. The analysis of the change of the electronic density integral value in each Basin given by the topological analysis of the electronic domain function during the reaction shows that the inner electrons do not participate in and affect the formation and fracture of the chemical bonds in the chemical reaction process and the C-H bond is more important. The chemical bond changes in the chemical reaction process are involved in a small degree. The fracture and formation of the covalent bond C-Cl has a quantitative relationship with the interaction of Cl soliton pair electrons, V (C-H4), V (C-H5), V (C-H6), which decreases with the decrease of V (C-Cl1) value and decreases with the increase of V (C-Cl3) values. The fracture increases with the gradual formation of the C-Cl3 bond, and the interaction between C and H is the strongest in the transition state. The value of L (Cl-1) increases with the decrease of the value of V (C-Cl1), and the value of L (Cl-3) decreases with the increase of V (C-Cl3). The fourth chapter is an electronic domain for the chemical reaction of SN2 system. The results show that the fracture of the C-Br bond and the formation of the O-C bond are carried out at the same time, but according to the variation analysis of the C-Br key domain V (C-Br) and the C-O key domain V (C-O) electron density integral value in the HO+CH_3Br to HOCH_3+Br IRC process, the fractured C-Br key is deposited as a covalent bond before the transition state is formed. In the form of the gradual formation of the O-C bonds in the form of the closure of the shell layer (not a typical covalent bond), after the formation of the transition state, the C-Br bond exists in the form of the closure of the shell layer, and the O-C bond exists in the form of covalent bonds; the electronic density integral value in all kinds of Basin derived by the electron fixed domain function in the reaction process is changed. The analysis shows that in the HO+CH_3Br to HOCH_3+Br reaction process, the inner electrons do not participate in and affect the formation and fracture of chemical bonds in the chemical reaction process. The C-H and O-H bonds are less involved in the chemical bond changes during the chemical reaction, the fracture of the covalent bond and the formation of the O-C and the existence of the Br, O atoms. In the quantitative electron transfer to each other.

【学位授予单位】：河北师范大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：O643.1

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