The atmospheric chemistry of organic nitrogen compounds (ONCs) is of great importance for understanding the formation of carcinogenic nitrosamines, and ONC oxidation products might influence atmospheric aerosol particle formation and growth. Indole is a polyfunctional heterocyclic secondary amine with a global emission quantity almost equivalent to that of trimethylamine, the amine with the highest atmospheric emission. However, the atmospheric chemistry of indole remains unclear. Herein, the reactions of indole with •OH and •Cl, and subsequent reactions of resulting indole radicals with O₂ under 200 ppt NO and 50 ppt HO₂• conditions, were investigated by a combination of quantum chemical calculations and kinetics modeling. The results indicate that •OH addition is the dominant pathway for the reaction of •OH with indole. However, both •Cl addition and H abstraction are feasible for the corresponding reaction with •Cl. All favorably formed indole radicals further react with O₂ to produce peroxy radicals, which mainly react with NO and HO₂• to form organonitrates, alkoxy radicals and hydroperoxide products. Therefore, the oxidation mechanism of indole is distinct from that of previously reported amines, which primarily form highly oxidized multifunctional compounds, imines or carcinogenic nitrosamines. In addition, the peroxy radicals from the •OH reaction can form N-(2-formylphenyl)formamide (C₈H₇NO₂), for the first time providing evidence for the chemical identity of the C₈H₇NO₂ mass peak observed in the •OH + indole experiments. More importantly, this study is the first to demonstrate that despite forming radicals by abstracting an H atom at the N site, carcinogenic nitrosamines were not produced in the indole oxidation reaction.

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●OH和●Cl引发的吲哚大气氧化机理和动力学：计算研究

有机氮化合物（ONCs）的大气化学对于了解致癌亚硝胺的形成非常重要，ONC氧化产物可能会影响大气气溶胶颗粒的形成和生长。吲哚是一种多官能团杂环仲胺，其全球排放量几乎与大气排放量最高的胺三甲胺相当。然而，吲哚的大气化学仍不清楚。在此，在 200 ppt NO 和 50 ppt HO ₂ •条件下，吲哚与• OH 和• Cl 的反应，以及所得吲哚自由基与 O _{2的后续反应}条件，通过结合量子化学计算和动力学建模来研究。结果表明• OH加成是• OH与吲哚反应的主要途径。然而，• Cl添加和H 提取对于与• Cl的相应反应都是可行的。所有有利形成的吲哚自由基进一步与O ₂反应生成过氧自由基，其主要与NO和HO _2反应•形成有机硝酸盐、烷氧基自由基和氢过氧化物产物。因此，吲哚的氧化机理不同于以往报道的胺，后者主要形成高度氧化的多功能化合物、亚胺或致癌亚硝胺。此外，• OH反应产生的过氧自由基可形成N-(2-甲酰基苯基)甲酰胺(C ₈ H ₇ NO ₂ )，首次为C ₈ H ₇ NO ₂质量峰的化学特性提供了证据。观察到 • OH  + 吲哚实验。更重要的是，本研究首次证明，尽管通过在 N 位提取 H 原子形成自由基，但在吲哚氧化反应中并未产生致癌亚硝胺。