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本文利用量子化学从头计算法(内禀反应坐标法)在3-21G基组上对乙炔与氢化锂二聚体的加成反应作了反应路径解析。确定了过渡态的结构、反应势能曲线、活化能、反应热以及沿着IRC的一些物理量的变化。研究结果表明:在乙炔与氢化锂二聚体的加成反应途径上,靠近孤立反应物存在一个准稳定的分子复合物状态,并且这个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单分子重排过程的频率因子和活化熵值。对反应过渡态的前线分子轨道分析表明:在过渡态的形成过程中,反应物系分子之间的HOMO-LUMO和HOMO-HOMO相互作用都起了重要作用。通过比较乙炔与氢化锂单体和二聚体两个加成反应的活化能、活化熵和反应频率因子,指出了这两个反应发生相互竞争的可能性。
In this paper, the adatom reaction of acetylene with lithium hydride dimer was performed on 3-21G basis set by quantum chemistry ab initio method (intrinsic reaction coordinate method). The structure of the transition state, the reaction potential curve, the activation energy, the heat of reaction and some physical quantities along the IRC are determined. The results show that there exists a quasi-stable molecular complex near the isolated reactants on the route of addition reaction of acetylene and lithium hydride dimer, and the elementary process of the molecular complex to form the product by single molecular rearrangement constitutes The rate of the reaction step. According to the RRKM theory, the frequency factor and activation entropy corresponding to the single molecular rearrangement process are also estimated. The frontier molecular orbital analysis of the reaction transition states shows that HOMO-LUMO and HOMO-HOMO interaction between the molecules of the reaction system play an important role in the transition state formation. By comparing the activation energies, activation entropy and reaction frequency factors of two addition reactions of acetylene with lithium hydride monomer and dimer, the possibility that these two reactions compete with each other is pointed out.