化学反应的内禀反应坐标法(Ⅳ)——乙炔与氢化锂1:2加成的反应路径解析

THE IRC METHOD IN CHEMICAL REACTIONS Ⅳ REACTION ERGODOGRAPHY FOR THE 1:2 ADDITION OF C_2H_2 TO LiH

本文用内禀反应坐标法在 RHF/3—21G 水平上对乙炔—氢化锂分子复合物与氢化锂的加成反应进行了量子化学从头计算研究,结果表明在此加成反应的势能曲线上存在一个由乙炔一氢化锂分子复合物与氢化锂进一步缔合而成的亚稳定的分子复合物状态,并且这个新的分子复合物经单分子重排生成产物的基元过程构成了该反应的定速步骤。根据 RRKM 理论还估算出相应于分子内重排过程的A 因子和活化熵值。前线分子轨道分析表明此加成反应途径上存在着两种三体相互作用形式的转变。

The ab initio calculation has been performed on the addition of acetylene—lithium hy- dride molecular complex to LiH at 3—21G basis set.The process from the molecular complex to product is the rate—controlling step of the reaction.by the transition state.By comparing the activa- tion energy and activation entrop of this reaction with that of the additions of LiH and its dimer to acetylene,We point out the possibility that these three reactions occur in a competing way in an ac- tual system.