Mull Henry F, Aroeira Gustavo J R, Turney Justin M, Schaefer Henry F
Center for Computational Quantum Chemistry, University of Georgia, 1004 Cedar Street, Athens, Georgia 30602, USA.
Phys Chem Chem Phys. 2020 Oct 15;22(39):22555-22566. doi: 10.1039/d0cp03781h.
Criegee intermediates are important targets for study in atmospheric chemistry because of their capacity to oxidize airborne species. Among these species, ammonia has received critical attention for its presence in polluted agricultural or industrial areas and its role in forming particulate matter and condensation nuclei. Although methylamine has been given less attention than ammonia, both theoretical and experimental studies have demonstrated that the additional methyl substitution on the ammonia derivatives increases the rate constants for some systems. This suggests that the methylamine addition to Criegee intermediates could be more significant to atmospheric processes. In this work, geometries are optimized at the DF-CCSD(T)/ANO1 level for the methylamine addition reactions to the simplest Criegee intermediate and the anti- and syn-methylated Criegee intermediates. Energies for each stationary point were computed at the CCSD(T)/CBS level with corrections from the CCSDT(Q) method. Rate constants are obtained for each reaction using canonical transition state theory. Although methylamine addition proved to be a more favorable reaction relative to ammonia addition, the significantly lower concentration of atmospheric methylamine limits the prevalence of these reactions, even in the most optimal conditions. It is unlikely that the methylamine addition to Criegee intermediates will contribute significantly to the consumption of Criegee intermediates in the atmosphere.
由于克里吉中间体能够氧化空气中的物质，因此它们是大气化学研究的重要目标。在这些物质中，氨因其在污染的农业或工业区中的存在以及其在形成颗粒物和凝结核中的作用而受到了密切关注。尽管甲胺受到的关注比氨少，但理论和实验研究均表明，氨衍生物上额外的甲基取代增加了某些体系的速率常数。这表明甲胺与克里吉中间体的反应对大气过程可能更为重要。在这项工作中，采用DF-CCSD(T)/ANO1方法对甲胺与最简单的克里吉中间体以及反式和顺式甲基化克里吉中间体的加成反应的几何结构进行了优化。使用CCSD(T)/CBS方法计算了每个驻点的能量，并采用CCSDT(Q)方法进行了校正。利用正则过渡态理论获得了每个反应的速率常数。尽管相对于氨的加成反应，甲胺的加成反应更为有利，但大气中甲胺的浓度显著较低，这限制了这些反应的普遍性，即使在最理想的条件下也是如此。甲胺与克里吉中间体的反应不太可能对大气中克里吉中间体的消耗产生显著贡献。
