Kjærgaard Eva R, Møller Kristian H, Berndt Torsten, Kjaergaard Henrik G
Department of Chemistry, University of Copenhagen, Universitetsparken 5, DK-2100 Copenhagen Ø, Denmark.
Atmospheric Chemistry Department (ACD), Leibniz Institute for Tropospheric Research (TROPOS), Permoserstraße. 15, 04318 Leipzig, Germany.
J Phys Chem A. 2023 Oct 19;127(41):8623-8632. doi: 10.1021/acs.jpca.3c04341. Epub 2023 Oct 6.
Autoxidation has been acknowledged as a major oxidation pathway in a broad range of atmospherically important compounds including isoprene and monoterpenes. More recently, autoxidation has also been identified as central and even dominant in the atmospheric oxidation of the rather small nonhydrocarbons dimethyl sulfide (DMS) and trimethylamine (TMA). Here, we find even faster autoxidation in the aliphatic amine triethylamine (TEA). The atmospherically dominating autoxidation leads to highly oxygenated and functionalized compounds. Products with as many as three hydroperoxy (OOH) groups and an O:C ratio larger than 1 are formed. We present theoretical multiconformer transition-state theory (MC-TST) calculations of the unimolecular reactions in the autoxidation following the OH + TEA reaction and calculate peroxy radical H-shift rate coefficients >20 s for the first two generations of H-shifts. The efficient autoxidation in TEA is verified by the observation of the proposed highly oxidized products and radicals in flow-tube experiments. We find that the initial OH hydrogen abstraction at the α-carbon is strongly favored, with the β-carbon abstraction yield being less than a few percent.
自氧化已被公认为包括异戊二烯和单萜在内的多种对大气重要的化合物的主要氧化途径。最近，自氧化也被确定为相当小的非碳氢化合物二甲基硫醚（DMS）和三甲胺（TMA）大气氧化的核心甚至主导途径。在此，我们发现脂肪族胺三乙胺（TEA）的自氧化速度甚至更快。大气中占主导的自氧化会生成高度氧化和官能化的化合物。会形成具有多达三个氢过氧基（OOH）且氧碳比大于1的产物。我们给出了OH + TEA反应后自氧化中单分子反应的理论多构象过渡态理论（MC-TST）计算结果，并计算了前两代氢转移的过氧自由基氢转移速率系数>20 s⁻¹。通过在流动管实验中观察到所提出的高度氧化产物和自由基，验证了TEA中的高效自氧化。我们发现，在α-碳处最初的OH氢提取非常有利，β-碳提取产率不到百分之几。
