CH_3NO_2+O[~3P]→CH_2NO_2+OH反应途径和速率常数的研究

Study on the Pathways and Variational Rate Constants of Reaction CH_3NO_2 + O[~3P]→CH_2NO_2 + OH

采用DFT(B3LYP)从头算法,在6 311G**和cc pvtz基组水平上,优化了CH3NO2+O[3P]→CH2NO2+OH反应的反应物、过渡态和产物的几何结构,结果表明,基组选择对驻点的几何构型影响很小.由B3LYP/cc pvtz计算所得的反应位垒为24.52 kJ/mol,比实验值22.38 kJ/mol大2.14 kJ/mol.沿内禀反应坐标(IRC)的分析指出,C—H键断裂和H—O键生成是以协同方式进行的,且在反应途径上存在一个引导反应进行的振动模式,这一振动模式引导反应进行的区间为S=-0.35~0.85(amu)1/2Bohr;在1 300~2 100 K范围内运用改进的变分过渡态理论(ICVT)计算出的该反应速率常数与实验结果一致.

The geometrical figure of the reactants, the transitional state and the products for reaction CH_3NO_2 + O [~3P]→CH_2NO_2 + OH were optimized at the level of 6-311G** and cc-pvtz basis by using DFT(B3LYP). The results showed that the selection of the basis had only minute effect on the geometric structures at the stationary geometries. The potential barrier calculated with B3LYP/cc-pvtz is 24.52kJ/mol, which is only (2.14kJ/mol)(more than) that of the experimental value 22.38kJ/mol. The analysis along IRC indicated that the breakage of C—H bond and formation of H—O bond was a concerted process, and furthermore along the reaction pathway there existed a vibrational mode which lead to successful reaction. The domain of the reaction promoted by the vibrational mode was S=-0.35—0.85 (amu)^(1/2)Bohr. The rate constant of the reaction calculated by using the improved canonical variational transition state theory(ICVT) was in agreement with that of the experimental value in the temperature range of 1300—2100K.