多叠氮基嗪异构化反应的密度泛函理论研究

Density Functional Theory Study on Tautomerization of Polyazido-azine

用密度泛函理论(DFT),对3,6-二叠氮基-1,2,4,5-四嗪(DiAT)和2,4,6-三叠氮基-1,3,5-三嗪(TAT)的叠氮→四唑异构化反应(关环反应)进行了研究。在B3LYP/6-311G**水平下优化了反应通道上各驻点(反应物、过渡态、产物)的几何构型,计算了各物种的总能量,并对总能量进行零点能校正。设计等键反应计算了各物种的生成焓,分析叠氮基向四唑环的转化对化合物分子构型、生成焓的影响。研究表明:3,6-二叠氮基-1,2,4,5-四嗪(DiAT)经两步环化反应生成四唑异构体,其反应能垒分别为100.5,117.4 kJ.mol-1。2,4,6-三叠氮基-1,3,5-三嗪(TAT)经三步环化反应生成四唑异构体,其反应能垒分别为101.8,99.7,108.7 kJ.mol-1。叠氮基环化为四唑环时,分子生成焓增大。从热力学上判断,TAT关环反应比DiAT关环反应更难进行。用自洽反应场(SCRF)方法对叠氮→四唑异构化反应进行溶剂化效应的计算,分析了二甲亚砜对分子性质的影响。

The tautomerizations of polyazido-azine（ring-closure reaction） for 3,6-diazido-1,2,4,5-tetrazine（DiAT） and 2,4,6-triazido-1,3,5-triazine（TAT） were investigated by density functional theory.All of the stationary points（reactants,transition states and products） on the reaction paths were optimized at the B3LYP/6-311G＊＊ level.The total energies were obtained after zero-point vibrational energy correction.Enthalpies of formation were derived via the designed isodesmic reactions.The changes of energies,geometries and enthalpies of formation in the tautomerization were analyzed.The cyclization of 3,6-diazido-1,2,4,5-tetrazine processes by two steps with energy barriers of 100.5 and 117.4 kJ·mol^-1,respectively,and the cyclization of 2,4,6-triazido-1,3,5-triazine by three steps with energy barriers of 101.8,99.7 and 108.7 kJ·mol^-1.The enthalpies of formation increase in the process of cyclizations.The ring-closure reaction of TAT is thermodynamically more unfavorable in comparison to that of DiAT.The solvent effect of dimethyl sulfoxide on the tautomerization was evaluated with the self-consistent reaction field（SCRF） method.