摘要
本文用内禀反应坐标(IRC)方法对甲硅硫醛分子异构化反应的微观反应动力学进行了研究.在RHF/4—31G基组上对此反应做了从头计算和反应路径解析,得到H_2SiS两种异构体的平衡几何,过渡态结构、反应势能曲线、活化能、反应热以及沿反应坐标一些物理量的变化,并对平衡几何和过渡态做了振动分析.同时,计算了反应频率因子A和在500K时的活化熵△S^(?)。将所得结果与甲硫醛H_2CS的情况作了对比。
The microscopic kinetics of the isomerization reaction of silathione H_2SiS was studied by means of intrinsic reaction coordinate (IRC) method. The reaction ergodography was analyzed by ab initio MO calculations on the RHF/4-31G basis set. The equilibrium structures of H_2SiS and trans—HSiSH were optimized which have the C_2, and C_3 symmetry, respectively. The transition state was also located which has no symmetry. The bond lengths of Si-S、 Si-H_1 and Si-H_2 are 2.158A. 1.627Aand 1.521 A, respectively. The bond angle of H_1SiS is 55.1° . The activation energy was calculated to be 82.08 kcal·mol^(-1) and the reaction heat is 15.88 kcal·mol^(-1). The change of some physical properties along the IRC were presented. The vibrational analyses of the reactant and the transition state have also been made. The reaction path was found has two characteristic stages: at the first one, the decrease of the bond angle H_1SiS is great; and at the second one, the stretching of the Si—H_1 bond is the major feature. Besides, the frequency factor A and the entropy of activation at 500K were estimated with the application of RRKM theory. All the results were compared with the same reaction of methanethial H_2CS.
基金
国家自然科学基金
