Bunkan Arne Joakim C, Tang Yizhen, Sellevåg Stig R, Nielsen Claus J
Centre for Theoretical and Computational Chemistry, Department of Chemistry, University of Oslo , P.O. Box 1033, Blindern 0315, Oslo, Norway.
J Phys Chem A. 2014 Jul 17;118(28):5279-88. doi: 10.1021/jp5049088. Epub 2014 Jul 8.
Quantum chemical methods were used to investigate the OH initiated atmospheric degradation of methanimine, CH2═NH, the major primary product in the atmospheric photo-oxidation of methylamine, CH3NH2. Energies of stationary points on potential energy surfaces of reaction were calculated using multireference perturbation theory and coupled cluster theory. The results show that hydrogen abstraction dominates over the addition route in the CH2═NH + OH reaction, and that the major primary product is HCN, while HNC and CHONH2 are minor primary products. HNC is found to react with OH exclusively via addition to the carbon atom followed by O-H scission leading to HNCO; N2O is not a product in the atmospheric photo-oxidation of HNC. Additional G4 calculations of the CH2═NH + O3 reaction show that this is too slow to be of importance at atmospheric conditions. Rate coefficients for the CH2═NH + OH and HNC + OH reactions were calculated as a function of temperature and pressure using a master equation model based on the coupled cluster theory results. The rate coefficients for OH reaction with CH2═NH and HNC at 1000 mbar and room temperature are calculated to be 3.0 × 10(-12) and 1.3 × 10(-11) cm(3) molecule(-1) s(-1), respectively. The atmospheric fate of CH2═NH is discussed and a gas phase photo-oxidation mechanism is presented.
采用量子化学方法研究了甲亚胺（CH2═NH）在OH引发下的大气降解过程，甲亚胺是甲胺（CH3NH2）大气光氧化的主要初级产物。利用多参考微扰理论和耦合簇理论计算了反应势能面上驻点的能量。结果表明，在CH2═NH + OH反应中，氢提取比加成途径占主导地位，主要初级产物是HCN，而HNC和CHONH2是次要初级产物。发现HNC与OH反应仅通过加成到碳原子上，随后发生O-H断裂生成HNCO；N2O不是HNC大气光氧化的产物。对CH2═NH + O3反应的额外G4计算表明，在大气条件下该反应太慢而不重要。使用基于耦合簇理论结果的主方程模型，计算了CH2═NH + OH和HNC + OH反应的速率系数随温度和压力的变化。在1000 mbar和室温下，OH与CH2═NH和HNC反应的速率系数分别计算为3.0×10(-12)和1.3×10(-11) cm(3) molecule(-1) s(-1)。讨论了CH2═NH的大气归宿并提出了气相光氧化机理。
