β-环糊精催化机理的理论研究

发布时间：2018-02-13 10:05

本文关键词： β-环糊精(β-CD) 催化密度泛函理论(DFT) 包合物　出处：《湘潭大学》2017年硕士论文　论文类型：学位论文

【摘要】：本文运用密度泛函理论(DFT)研究了β-环糊精(β-CD)的催化机理。包括:(1)β-环糊精催化邻苯二胺和苯甲醛的反应;(2)β-环糊精催化对硝基苯基乙酸酯与α-丙氨酸的反应;(3)β-环糊精催化2-溴苯乙酮与硫代苯甲酰胺的反应。第一,在β-CD催化作用下,邻苯二胺和苯甲醛转化生成2-苯基苯并咪唑的反应效率显著提高,用密度泛函理论对反应机理进行了研究。根据能量参数(相互作用能,变形能)和结构变化,判断各反应物进入环糊精包合的先后顺序及其反应过程(邻苯二胺以氨基为首端从环糊精的大口端进入形成包合物,苯甲醛以苯环为首端从小口端进入邻苯二胺和环糊精的包合物中)。前线分子轨道理论(HOMO-LUMO)、福井(Fukui)函数和Mulliken电荷分布,综合自然键轨道理论(NBO)与核磁共振波谱(NMR)揭示反应过程中的电子转移,并由此推测出可能存在的反应机理。结果表明,反应过程中在β-CD作用下反应的选择性和活性得到提高。第二,实验表明,在β-环糊精参与下,对硝基苯基乙酸酯和α-丙氨酸的反应速率能显著地提高,环糊精的催化作用明显。我们主要用密度泛函理论讨论了β-环糊精与对硝基苯基乙酸酯之间的相互作用,并推测了可能的反应机理。根据能量(相互作用能,变形能)参数和结构变化,确定客体分子的反应模型和反应过程(对硝基苯基乙酸酯以硝基为首端从β-环糊精的大口端进入空腔),通过前线分子轨道(HOMO-LUMO),Dual descriptor(DD),氢键和核磁共振波谱(NMR)等的分析揭示电子的转移,从而推断可能的反应机理。计算结果表明β-CD在对硝基苯基乙酸酯与α-丙氨酸的反应中起了催化作用,提高了反应速率和选择性。第三,实验证明在β-环糊精作用下,溴苯乙酮和硫代酰胺类的反应速率和产率有所提高。着重研究了两个客体分子与环糊精分别进行包合的可能性,以及包合物性质的变化。根据2-溴苯乙酮和硫代苯甲酰胺分别与环糊精包合的优化分析,确定两者包合后最稳定的构型,结合前线分子轨道,Mulliken电荷,核磁共振波谱等分析包合后两者的相互作用和结构变化。计算结果表明环糊精在与客体分子包合后两者的化学环境都发生变化,客体分子中主要基团的电荷密度发生改变。计算结果与实验结果一致,并推测了可能存在的反应机理。
[Abstract]:The catalytic mechanism of 尾 -cyclodextrin (尾 -CD) was studied by using density functional theory (DFT), including the reaction between o-phenylenediamine and benzaldehyde catalyzed by 尾 -cyclodextrin and 尾 -cyclodextrin catalyzed by p-nitrophenylacetate and 伪 -alanine. Catalytic reaction of 2-bromoacetophenone with thiobenzamide. First, The conversion efficiency of o-phenylenediamine and benzaldehyde to 2-phenylbenzimidazole was improved significantly under the catalysis of 尾 -CD. The reaction mechanism was studied by density functional theory. Deformation energy) and structural changes were used to determine the order in which the reactants entered cyclodextrin inclusion and the reaction process (o-phenylenediamine entered the inclusion complex from the big mouth of cyclodextrin at the end of amino group). Benzaldehyde leads from the end of benzene ring into the inclusion compound of o-phenylenediamine and cyclodextrin from the small end. The frontier molecular orbital theory of HOMO-LUMOA, Fukui (Fukui) function and Mulliken charge distribution, The electron transfer in the reaction process was revealed by combining the natural bond orbital theory (NBO) with nuclear magnetic resonance spectroscopy (NMR), and the possible reaction mechanism was inferred. The selectivity and activity of the reaction under the action of 尾 -CD were improved. Secondly, the reaction rate of p-nitrophenyl acetate and 伪 -alanine was significantly increased with the participation of 尾 -cyclodextrin. The catalytic effect of cyclodextrin is obvious. We mainly discuss the interaction between 尾 -cyclodextrin and p-nitrophenyl acetate by density functional theory, and speculate the possible reaction mechanism. Deformation energy) parameters and structural changes, The reaction model and reaction process of the guest molecule (p-nitrophenyl acetate entering the cavity from the large mouth of 尾 -cyclodextrin at the nitro-headed end, and the electron transfer revealed by the analysis of the front molecular orbital HOMO-LUMOMOTOR-DUMOTOR DDD, hydrogen bond and nuclear magnetic resonance spectroscopy (NMRs), etc.). The calculated results show that 尾 -CD plays a catalytic role in the reaction of p-nitrophenyl acetate with 伪 -alanine, and improves the reaction rate and selectivity. Thirdly, it is proved that 尾 -CD acts under the action of 尾 -cyclodextrin. The reaction rate and yield of bromoacetophenone and thioamides were improved. The possibility of inclusion of two guest molecules with cyclodextrin was studied. According to the optimized analysis of the inclusion of 2-bromoacetophenone and thiobenzamide with cyclodextrin, the most stable configuration of the inclusion was determined and the Mulliken charge was combined with the frontier molecular orbital. The results show that the chemical environment of cyclodextrin changes after inclusion with guest molecules. The charge density of the main groups in the guest molecule is changed. The calculated results are in agreement with the experimental results and the possible reaction mechanism is deduced.
【学位授予单位】：湘潭大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：O636.1;O621.251

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