NHO催化二氧化碳与炔丙醇和环氧化物生成环碳酸酯机理的理论研究

发布时间：2019-01-12 17:10

【摘要】：二氧化碳被认为是温室效应的主要来源,合理利用二氧化碳不仅能减弱环境问题,而且对缓解能源危机有重大的意义。但是二氧化碳的化学惰性阻碍了它在化学反应中的应用。近年来,越来越多的人们开始关注并探索能使二氧化碳活化的试剂,并且将其作为原材料与其他简单有机物反应合成具有化学利用价值的各种有机化合物。本文中我们使用Gaussion09程序,运用量子力学密度泛函理论(DFT)中的B3LYP方法,对NHO催化二氧化碳与炔丙醇和环氧化物反应生成环碳酸酯的机理分别进行了详细的研究和讨论。结果如下:1)NHO催化二氧化碳与炔丙醇反应生成环碳酸酯的机理对于NHO催化二氧化碳和炔丙醇生成环碳酸酯的反应,我们用DFT理论计算中B3LYP的方法,6-311+G(d,p)的基组,结合极化连续介质模型PCM考虑溶剂化效应,在溶剂DCM中对反应中涉及到的所有结构进行优化和频率分析,以及考虑了DFT-D3模型的色散校正,对反应机理进行了详细研究和讨论。该反应总共有六个机理,其中四个机理(M-A,M-B,M-B’和M-C)是关于生成五元环碳酸酯的,由DCM溶剂中的能量图可以看出,相对于初始反应物,它们的最高鞍点分别是45.37、31.99、57.07、35.11kcal/mol。另外两个机理(M-D和M-E)是关于生成六元环碳酸酯的,这两条路径的最高鞍点的相对能量比初始反应物分别高35.18、59.61kcal/mol。因此,机理M-B是整个反应的最优机理,具有最低的反应势垒31.99kcal/mol,机理M-C和M-D是与机理M-B进行动力学竞争的机理。然而,M-A,M-B’和M-E机理具有非常高的反应活化能,分别为45.37,57.07和59.61kcal/mol,表明这三个机理在整个反应中是次要的。而产物P1比P2的稳定性强,因此P1是主要产物,这与实验事实相符。2)NHO催化二氧化碳与环氧化物反应生成环碳酸酯的机理我们采用B3LYP的方法,6-311G(d,p)的基组,考虑PCM模型的溶剂化效应(DCM)以及DFT-D3模型的色散校正,对NHO催化二氧化碳和环氧化物生成环碳酸酯的反应机理进行了详细研究和讨论。该反应包括两个反应机理(M-1和M-2),机理M-1与M-2反应机理的不同在于:在机理M-1中,催化剂NHO先与环氧化物加成开环,后与二氧化碳发生加成反应;而在M-2中,催化剂NHO首先与二氧化碳加成再与环氧化物开环加成。机理M-1由三个反应步骤组成,二氧化碳的加成反应是无势垒的,其中最后一步的势垒(40.33kcal/mol)最高,是整个反应的决速步。机理M-2包括四个反应步骤,第三步具有最高势垒32.74kcal/mol,是整个路径的最高鞍点。机理M-1和M-2在动力学上是相互竞争的,而由于机理M-2的决速步势垒比机理M-1的低,所以机理M-2是较优机理。
[Abstract]:Carbon dioxide is considered to be the main source of Greenhouse Effect, the rational use of carbon dioxide can not only reduce environmental problems, but also have great significance in alleviating the energy crisis. But the chemical inertia of carbon dioxide hinders its application in chemical reactions. In recent years, more and more people begin to pay attention to and explore the reagent that can activate carbon dioxide, and use it as raw material to react with other simple organic compounds to synthesize various organic compounds with chemical utilization value. In this paper, using the Gaussion09 program and the B3LYP method in the density functional theory (DFT) of quantum mechanics, the mechanism of the reaction of carbon dioxide with propargyl alcohol and epoxide by NHO has been studied and discussed in detail. The results are as follows: 1) the mechanism of the reaction between carbon dioxide and propargyl alcohol catalyzed by NHO to form cyclocarbonate is discussed. The method of B3LYP in DFT theory, 6-311 G (d, is used to calculate the reaction of NHO with carbon dioxide and propargyl alcohol to form cyclocarbonate. P), considering solvation effect, optimization and frequency analysis of all the structures involved in the reaction in solvent DCM, and considering dispersion correction of the DFT-D3 model, in combination with the polarimetric continuum model (PCM). The reaction mechanism was studied and discussed in detail. The reaction consists of six mechanisms, four of which are related to the formation of pentacyclic carbonates, four of which are related to the formation of pentacyclic carbonates, as can be seen from the energy diagram in the DCM solvent, as compared with the initial reactants. Their highest saddle points are 45.37731.99 kcal / mol, 57.07N 35.11kcal / mol, respectively. The other two mechanisms (M-D and M-E) are related to the formation of hexacyclic carbonate. The relative energy of the highest saddle point of these two paths is 35.18 ~ 59.61 kcal / mol higher than that of the initial reactant, respectively. Therefore, the mechanism M-B is the optimal mechanism of the whole reaction, with the lowest reaction barrier of 31.99kcal / mol, and the mechanisms M-C and M-D are the mechanism of kinetic competition with the mechanism M-B. However, M-An M-B 'and M-E mechanisms have very high activation energies of 45.37 and 59.61 kcal / mol, respectively, indicating that these three mechanisms are of secondary importance in the whole reaction. The stability of product P1 is stronger than that of P2, so P1 is the main product, which is consistent with the experimental facts. 2) the mechanism of NHO catalyzing the reaction of carbon dioxide with epoxide to produce epoxide. We adopt the method of B3LYP, the base group of 6-311G (dapp). Considering the solvation effect of the PCM model (DCM) and the dispersion correction of the DFT-D3 model the reaction mechanism of the formation of epoxycarbonate from carbon dioxide and epoxide catalyzed by NHO was studied and discussed in detail. The reaction consists of two reaction mechanisms (M-1 and M-2). The mechanism of M-1 and M-2 is different from that of M-1. In mechanism M-1, the catalyst NHO is added to epoxide first and then to carbon dioxide. In M-2, the catalyst NHO was first added to carbon dioxide and then to epoxide. Mechanism M-1 is composed of three reaction steps. The addition of carbon dioxide is barrier free, and the 40.33kcal/mol of the last step is the highest, which is the fast step of the whole reaction. Mechanism M-2 consists of four steps. The third step has the highest barrier 32.74 kcal / mol, which is the highest saddle point of the whole path. The kinetics of mechanism M-1 and M-2 is competitive with each other, but the mechanism M-2 is a better mechanism because the barrier of mechanism M-2 is lower than that of mechanism M-1.
【学位授予单位】：山西师范大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：O624.5

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