CH_3自由基与CH_3NH_2抽氢反应的动力学研究

Kinetic calculation on the hydrogen abstraction reaction between CH_3 radical and CH_3NH_2

用QCISD（T）／6—311＋＋G（d，p）／／MP2（full）／6—311G（d，P）方法研究了CH3自由基与CH3NH2的抽氢反应过程．结果表明，该反应包含两个反应通道，即CH3分别从CH3基团（R1）和NH2（R2）基团上抽氢、R1势垒比R2势垒仅低3.42kJ／mol，表明两反应通道将相互竞争．在从头算的基础上，用变分过渡态理论（CVT）加小曲率隧道效应（SCT）研究了各反应在温度范围为200～2000K内的速率常数，所得结果与实验值符合的较好．动力学计算表明，在所研究的温度范围内．变分效应对速率常数的计算影响不大．而在低温范围内．隧道效应起了很重要的作用。

Hydrogen abstraction reaction between CH3 radical and CH3NH2 is explored using the QCISD（T）/6 - 311 ＋ ＋ G（d, p）//MP2 （full）/6 - 311G（d, p） method. This reaction takes place through two channels： CH3 abstraction from methyl group （CH3） （R1） and amido group （NH2） （R2）. The potential barrier of R1, about 3.42 kJ/mol, is lower than that of R2, which shows that two reaction channels will compete mutually. On the basis of the ab initio data, the rate constants for each channel were evaluated using canonical variational transition state theory （CVT） with the smallcurvature tunneling correction （SCT） method over a wide temperature range of 200-2 000 K. The total rate constants are excellent to agree with the experimental values. The kinetic calculation indicates that the variational effect on the calculation of rate constants is small over the whole temperature range and the tunneling correction plays an important role in the lower temperature range for all the channels.