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辣椒碱(Capsaicin)在医药、农业和反恐装备方面具有广泛的应用前景。本文用密度泛函理论DFT/B3LYP方法,在6-31+G(d,p)基组水平上对其进行了计算。密度泛函理论方法既考虑了电子相关,又较其他组态相互作用或微扰方法节省机时,其计算结果可靠,被广泛应用于研究各类化合物结构性质。本文获得了辣椒碱分子稳定的几何构象和电荷分布,确定O(12)、N(16)、O(19)、C(37)和C(38)原子,可以作为氢键受体;C(18)与O(19)原子形成一对偶极,它们均是关键药效团的活性部位。通过进行分子轨道特征分析,确定苯环区是参加化学反应时的活性部位。进行的自然键轨道分析结果与分子轨道特征分析结论一致。在振动分析的基础上获得分子的振动频率、IR光谱与实验结论一致;在振动分析的基础上,同时获得不同温度下的热力学性质以及温度对热力学性能影响的关系式,其中,当T>2 542 K时,热容C_(p,m)~θ会随温度的升高而减小,各表达式和热力学量对深入研究辣椒碱分子的其它热力学性质有帮助。探讨了辣椒碱热分解机理,获得该分子热分解时C-N键的断裂能为306.6 kJ·mol~(-1)。本文为研究辣椒碱类化合物的定量构效关系研究提供理论依据。
Capsaicin has a wide range of applications in medicine, agriculture and anti-terrorism equipment. In this paper, density functional theory DFT / B3LYP method, 6-31 + G (d, p) group level of its calculation. Density functional theory (DFT), which takes into account both electron correlation and mechanical confidentiality when compared with other configurations or perturbation methods, is reliable and has been widely used to study the structural properties of various compounds. In this paper, the geometrical conformations and charge distributions of capsaicin molecules were obtained, and O (12), N (16), O (19), C (37) and C (38) 18) forms a pair of dipoles with the O (19) atom, all of which are the active sites of the key pharmacophore. By analyzing molecular orbital characteristics, it was confirmed that the benzene ring region was the active site when participating in the chemical reaction. The results of the natural bond orbital analysis are consistent with the molecular orbital characteristics analysis. On the basis of the vibration analysis, the thermodynamic properties at different temperatures and the relationship between the temperature and the thermodynamic performance were also obtained. When T> 2 At 542 K, the heat capacity C_ (p, m) ~ θ decreases with increasing temperature. The expressions and thermodynamic quantities are helpful to further study on other thermodynamic properties of capsaicin molecules. The mechanism of thermal decomposition of capsaicin was explored. The fracture energy of C-N bond was 306.6 kJ · mol ~ (-1) when the molecule was thermally decomposed. This article provides a theoretical basis for the study of quantitative structure-activity relationship of capsaicinoids.