Theoretical Research on the Multi-channel Reaction Mechanism of CHF Radical with HNCO by Density Functional Theory

The reaction mechanism of CHF radical with HNCO was investigated by the B3LYP method of density functional theory （DFT）, while the geometries and harmonic vibration frequencies of reactants, intermediates, transition states and products were calculated at the B3LYP/6-311＋＋G＊＊ level. In the temperature range of 100-2600 K, the statistical thermody- namics and Eyring transition state theory with Winger correction were used to study the thermodynamic and kinetic characters of the channel with low energy barrier. In addition, the analysis on the combining interaction between CHF radical and HNCO was performed by atom-in-molecules theory （AIM） and natural bond orbitals （NBO） analysis. The calculation results indicated that the reaction of CHF radical with HNCO had ten channels, and the channel of NH direct extraction （CHF ＋ HNCO→IM6→TS7→IM7→CHFNH ＋ CO） in singlet state was the main channel with low potential energy and high equilibrium constant and reaction rate constant. CHFNH and CO were the main products.

密度泛函理论研究SiFCl自由基和异硫氰酸的反应机理

采用密度泛函理论(DFT)的B3LYP方法对SiFCl自由基和HNCS的反应机理进行研究,在B3LYP/6-311++G**水平上对反应势能面上的所有稳定点(反应物、过渡态和中间体)进行了全几何参数优化,通过简谐振动频率分析和內禀反应坐标(IRC)确定中间体和过渡态。应用G3方法计算了在B3LYP/6-311++G**水平优化后的各个驻点的相对能量以获得更精确的能量值,化学反应过程中主要化学键的生成和断裂通过自然键轨道理论(NBO)和电子密度拓扑分析(AIM)进行详细讨论;依据统计热力学和用Winger校正的Eyring过渡态理论,计算了低势垒反应在不同温度下的平衡常数和速率常数。结果表明,单重态的SiFCl自由基与HNCS的反应有8条可能的反应通道,其中单重态反应通道SiFCl+HNCS→IM5→TS7→SSiFClCNH(P2)为主反应通道。