CH_3CH_2自由基与HNCO反应机理的理论研究

Theoretical Study on the Reaction Mechanism of CH_3CH_2 Radical with HNCO

采用密度泛函理论的B3LYP方法,在6-311++G(d,p)基组水平上研究了CH3CH2自由基与HNCO的微观反应机理,优化了反应过程中的反应物、中间体、过渡态和产物,为了获得更精确的能量信息,在QC ISD(T)/6-311++G(d,p)水平上计算体系在反应通道各驻点的能量.振动分析结果和IRC分析结果证实了中间体和过渡态的真实性,计算所得的成键临界点电荷密度变化也确认了反应过程.对于CH3CH2自由基与HNCO反应,找到了10条反应通道.对结果的分析表明,其中生成烷基酰亚胺稳定分子的反应通道的控制步骤活化能最低,因此为主要通道,在该反应体系中氢迁移反应已不是主要的反应过程,但其活化能不高,也是能发生的.

The reaction mechanism of CH3CH2 radical with HNCO has been investigated by density functional theory （DFT）. The geometries and frequencies of reactants, intermediates, transition states and products have been calculated at the B3LYP/6-311 ＋ ＋ G （d, p） level. To obtain more accurate energy results, single point energies were also calculated at the QCISD （T）/6-311 ＋ ＋ G （d, p） level. The vibration analysis and the IRC analysis approved the authenticity of intermediates and transition states, and the reaction processes were confirmed by the changes of charge density at bond-forming critical points. Seven feasible reaction pathways of this reaction have been found and studied. The results indicate that the main pathway is the one which produces the stable molecule alkyl imide, not the hydrogen transfer process. In the reaction system, the activation energy in the process of the hydrogen transfer is not very high. so this orocess also can take olace.