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本文用SCF MO ab initio法研究了环氧乙烷与NH_2~-的亲核置换反应.用能量梯度优化方法(辅以可变尺度法)优化出了反应物与产物的平衡几何构型,与实验对应较好.用Powell的对梯度的Euclidean范数σ求极小的方法优化出了过渡态几何构型,并从过渡态的力常数矩阵求得了相应于反应坐标的频率为821icm~(-1),从而对求出的过渡态进行了确证.用STO-3G基组求出该反应的活化能为44.50kJ·mol~(-1).由过渡态和产物的几何构型得出NH_2~-基本上沿环氧乙烷的“弯键”方向进攻.将过渡态看成由变形后的反应物分子与进攻试剂形成的“超分子”,用Morokuma的能量分解方案对它们之间的相互作用能进行分解,得出了电荷迁移相互作用和静电相互作用在反应中都起重要作用的结论.
In this paper, the nucleophilic displacement of ethylene oxide with NH_2 ~ - was studied by the SCF MO ab initio method. The equilibrium geometry of reactants and products was optimized by the energy gradient optimization method The experimental results show that the transition state geometry is optimized by Powell’s Euclidean norm σ of the gradient and the frequency corresponding to the reaction coordinate is found to be 821 icm ~ (- 1) to confirm the transition state obtained.The activation energy of the reaction was calculated to be 44.50kJ · mol -1 by using STO-3G basis set.From the transition state and the geometry of the product, NH_2 ~ - essentially attacking in the “bend bond” direction of ethylene oxide.The transition state is considered as the “supramolecule” formed by the deformed reactant molecules and the attacking agent, with Morokuma’s energy resolution scheme between The interaction can be decomposed, and the conclusion is drawn that charge transfer interaction and electrostatic interaction play an important role in the reaction.