H原子与CH3NH2抽氢反应的动力学计算

用QC ISD(T)/6-311 G(3DF,3PD)/MP2/6-311G(D,P)方法研究了H原子与CH3NH2的抽氢反应过程。该反应包含两个反应通道:H分别从CH3基团(R1)和NH2(R2)基团上抽氢。R1势垒比R2势垒低3.42kJ/mol,表明R1是主反应通道。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)研究了各反应温度范围为200~4000K内的速率常数,所得结果与实验值符合的很好。动力计算表明,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。

Kinetic calculation on the hydrogen abstraction reaction between H and CH3NH2

Hydrogen abstraction reaction between H and CH_3NH_2 is explored using the QCISD(T)/6-311 G(3df,3pd)//MP2/6-311 G(d,p) method.This reaction takes place through two channels:H abstraction from methyl group(CH_3)(R1)and amido group(NH_2)(R2).The potential barrier of R1 is about 17.41 kJ/mol lower than that of R2,which shows R1 is the major reaction channels.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 200~4000 K.The total rate constants are in excellent agreement 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 trnneling correction plays an important role in the lower temperature range for all the channels.