Xia Yu, Long Bo, Liu Ai, Truhlar Donald G
College of Materials Science and Engineering, Guizhou Minzu University, Guiyang 550025, China.
Department of Chemistry, Chemical Theory Center, and Minnesota Supercomputing Institute, University of Minnesota, Minneapolis, MN 55455-0431, United States.
Fundam Res. 2023 Mar 7;4(5):1216-1224. doi: 10.1016/j.fmre.2023.02.012. eCollection 2024 Sep.
Atmospheric oxidation processes are of central importance in atmospheric climate models. It is often considered that volatile organic molecules are mainly removed by hydroxyl radical; however, the kinetics of some reactions of hydroxyl radical with volatile organic molecules are slow. Here we report rate constants for rapid reactions of formyl fluoride with Criegee intermediates. These rate constants are calculated by dual-level multistructural canonical variational transition state theory with small-curvature tunneling (DL-MS-CVT/SCT). The treatment contains beyond-CCSD(T) electronic structure calculations for transition state theory, and it employs validated density functional input for multistructural canonical variational transition state theory with small-curvature tunneling and for variable-reaction-coordinate variational transition state theory. We find that the M11-L density functional has higher accuracy than CCSD(T)/CBS for the HC(O)F + CHOO and HC(O) + -CHCHOO reactions. We find significant negative temperature dependence in the ratios of the rate constants for HC(O)F + CHOO/-CHCHOO to the rate constant for HC(O) + OH. We also find that different Criegee intermediates have different rate-determining-steps in their reactions with formyl fluoride, and we find that the dominant gas-phase removal mechanism for HC(O)F in the atmosphere is the reaction with CHOO and/or -CHCHOO Criegee intermediates.
大气氧化过程在大气气候模型中至关重要。通常认为挥发性有机分子主要通过羟基自由基去除；然而，羟基自由基与挥发性有机分子的一些反应动力学很慢。在此，我们报告了甲酰氟与Criegee中间体快速反应的速率常数。这些速率常数通过具有小曲率隧道效应的双水平多结构正则变分过渡态理论（DL-MS-CVT/SCT）计算得出。该处理包含用于过渡态理论的超越耦合簇单双激发组态相互作用并包含微扰三重激发（CCSD(T)）水平的电子结构计算，并且它采用经过验证的密度泛函输入用于具有小曲率隧道效应的多结构正则变分过渡态理论以及可变反应坐标变分过渡态理论。我们发现对于HC(O)F + CHOO和HC(O) + -CHCHOO反应，M11-L密度泛函比CCSD(T)/完全基组外推（CBS）具有更高的精度。我们发现HC(O)F + CHOO/-CHCHOO速率常数与HC(O) + OH速率常数之比存在显著的负温度依赖性。我们还发现不同的Criegee中间体与甲酰氟反应的速率决定步骤不同，并且我们发现大气中HC(O)F的主要气相去除机制是与CHOO和/或-CHCHOO Criegee中间体的反应。
