Church Jonathan R, Vaida Veronica, Skodje Rex T
Department of Chemistry , University of Colorado , Boulder , Colorado 80309-0215 , United States.
J Phys Chem A. 2020 Feb 6;124(5):790-800. doi: 10.1021/acs.jpca.9b09638. Epub 2020 Jan 23.
The gas-phase reaction of pyruvic acid (PA) with the OH radical is studied theoretically using accurate quantum chemistry and transition state theory. Two chemically distinct H-atom abstraction reactions and two distinct OH addition reactions have been identified. The rate coefficients for these four processes were calculated. Quantum tunneling was included in each rate using the small curvature tunneling method. The influence of the conformational structure of PA was found to be particularly intriguing. While the trans-cis structure was found to dominantly react by H-atom abstraction from the methyl site, the trans-trans conformer was found to react mostly through H-atom abstraction from the acid site. A general formalism was developed to model the kinetics of the reactions that involve multiple conformers, interconverting prereactive complexes, and multiple transition states. Comparison of the results obtained with available experimental rate observations reveals agreement with the trans-trans conformer of PA but disagreement with the results obtained for a full statistical mixture of reagents. The role of these reactions in the atmospheric processing of PA is discussed.
利用精确的量子化学和过渡态理论，对丙酮酸（PA）与羟基自由基的气相反应进行了理论研究。已确定了两种化学性质不同的氢原子提取反应和两种不同的羟基加成反应。计算了这四个过程的速率系数。在每个速率计算中使用小曲率隧穿方法纳入了量子隧穿效应。发现PA的构象结构的影响特别有趣。虽然发现反-顺结构主要通过从甲基位点提取氢原子进行反应，但发现反-反构象体大多通过从酸位点提取氢原子进行反应。开发了一种通用形式来模拟涉及多个构象体、相互转化的预反应复合物和多个过渡态的反应动力学。将所得结果与现有的实验速率观测结果进行比较，发现与PA的反-反构象体相符，但与完全统计混合试剂所得结果不一致。讨论了这些反应在PA大气处理中的作用。
