5-卤代1,2,3,-三唑互变异构的密度泛函理论研究

DFT studies on the tautomerization of 1,2,3-triazoles and 5-halogeno-1,2,3-triazoles

用密度泛函B3LYP/6-311++G**方法,对气相和水相中的1,2,3三,-唑及5-卤(-F、C l和-B r)代1,2,3,-三唑互变异构体进行了几何构型全自由度优化,获得了它们在气相和水相中的几何结构和电子结构。计算结果显示,在气相和水相中1,2,3三-唑和5-卤代1,2,3三-唑的N2-H型要比对应的N1-H型和N3-H型稳定。讨论了不同的取代基团和溶剂化效应对互变异构体的几何结构、能量和电荷分布以及互变异构反应活化能的影响带。并进一步研究了N1-H、N2-H和N3-H型三唑之间的互变异构机理:(a)分子内质子转移;(b)水助质子转移。计算结果表明,途径(b)所需要的活化能较小,为120.06KJ/mol,途径(a)为204.12KJ/mol。

Molecular structures of 1,2,3 - triazoles and C5 - halogeno - triazole tautomers were calculated by the B3LYP method at the 6 - 311 ＋ ＋ G^＊＊ level both in the gaseous and aqueous phases with full geometry optimization. The geometrical and electronic structure of the tautomers of 1,2,3 -triazoles and C5 -halogeno- triazole and their transition states were obtained. The results of the calculation indicated that N2 - H tautomers form is more stable than that of N1 - H and N3 - H forms. The influence of the different 5 - halogeno and solvent effect on the geometrical structure,energy,charge,and activated energy were discussed. The reaction mechanism of tautomers of 1,2,3 - triazoles and CS - halogeno - triazole were also studied. There are two reaction pathways： （a） intramolecular proton transfer; （b） water - assisted intermolecular transfer. The calculated results showed that process in（b） has lower activation energies than （a）.