单重态二溴卡宾和甲醛环加成反应的量化研究

采用量子化学密度泛函理论,研究了单重态二溴卡宾和甲醛环加成反应的机理.在B3LYP/6-31G*基组水平上,优化得到了反应途径上反应物、过渡态、中间体和产物的几何构型;计算并考察了四种可能反应途径势能面上各驻点的构型参数、振动频率和能量;通过振动分析对过渡态和中间体构型进行了确认.计算结果表明,二溴卡宾和甲醛反应有四条反应通道,其中c反应通道(即0°-0°型)控制步骤的活化能仅为13.7 kJ·mol－1,反应容易进行.

Quantum Chemistry Study on the Cycloaddition Reaction of Dibromocarbene and Formaldehyde

The mechanisms of cycloaddition reactions of singlet dibromocarbene and formaldehyde have been studied using density functional theory of quantum chemistry method at B3LYP/6-31G* level. The geometrical parameters, harmonic vibrational frequencies and energies of stationary points on the potential energy surface are calculated. The structures of the stationary points were optimized, and the intermediates and transition states were detected by the frequency analysis. The calculation results show that the reaction has four possible reaction pathways. According to the data of the activation energy, we predict that path c would be the major reactive channel of the cycloaddition reactions of singlet dibromocarbene with formaldehyde, which proceeds in three steps and the energy barrier for the key step is 13.7 kJ·mol－1.