氢抽提反应CHBr_2+HBr→CH_2Br_2+Br的直接动力学研究

Direct dynamic study on the hydrogen abstraction reaction of CHBr_2+HBr→CH_2Br_2+Br

采用直接动力学方法,对CHBr2+HBr→CH2Br2+Br反应通道进行了理论研究,在B3LYP/6-311+G(d,p)水平下获得了优化几何构型、频率以及最小能量路径,更精确的单点能在B3LYP/6-311++G(3df,2pd)水平下完成.利用正则变分过渡态理论,结合小曲率隧道效应校正方法计算了反应通道在220 K^2 000 K温度范围内的速率常数.在整个反应区间,隧道效应对反应的影响比较大;变分效应在低温时有一定的影响,在高温区间的影响很小可以忽略.计算得到的速率常数和已有实验值很好地吻合.

Theoretical investigation is carried out on the hydrogen abstraction reaction of CHBr2＋HBr→CH2Br2＋Br by means of direct dynamic methods. The optimized geometries, frequencies, and minimum energy path is obtained at the B3LYP/6-311 ＋ G（ d ,p） level, and more reliable single point energy is calculated at the B3LYP/6-311 ＋＋ G （3 df, 2pd） level. The rate constant for the title reaction is calculated by canonical variational transition state theory with small curvature tunneling correction over the temperature range of 220 K ~ 2 000 K. The result shows that the tunneling effect is significant over the whole temperature region. The variational effect is small at the lower temperature, while it can be negligible at higher temperature. The theoretical rate constant is in reasonable agreement with available experimental data.