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Insights into the Peroxide-Bicyclic Intermediate Pathway of Aromatic Photooxidation: Experimental Yields and NOx-Dependency of Ring-Opening and Ring-Retaining Products
Environmental Science & Technology ( IF 10.8 ) Pub Date : 2023-11-29 , DOI: 10.1021/acs.est.3c05304 Shuyu He 1 , Ying Liu 1 , Mengdi Song 1 , Xin Li 1 , Sihua Lu 1 , Tianzeng Chen 2 , Yujing Mu 2 , Shengrong Lou 3 , Xiaodi Shi 1 , Xinghua Qiu 1 , Tong Zhu 1 , Yuanhang Zhang 1
Environmental Science & Technology ( IF 10.8 ) Pub Date : 2023-11-29 , DOI: 10.1021/acs.est.3c05304 Shuyu He 1 , Ying Liu 1 , Mengdi Song 1 , Xin Li 1 , Sihua Lu 1 , Tianzeng Chen 2 , Yujing Mu 2 , Shengrong Lou 3 , Xiaodi Shi 1 , Xinghua Qiu 1 , Tong Zhu 1 , Yuanhang Zhang 1
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Aromatic hydrocarbons are important contributors to the formation of ozone and secondary organic aerosols in urban environments. The different parallel pathways in aromatic oxidation, however, remain inadequately understood. Here, we investigated the production yields and chemical distributions of gas-phase tracer products during the photooxidation of alkylbenzenes at atmospheric OH levels with NOx present using high-resolution mass spectrometers. The peroxide-bicyclic intermediate pathway emerged as the major pathway in aromatic oxidation, accounting for 52.1 ± 12.6%, 66.1 ± 16.6%, and 81.4 ± 24.3% of the total OH oxidation of toluene, m-xylene, and 1,3,5-trimethylbenzene, respectively. Notably, the yields of bicyclic nitrates produced from the reactions of bicyclic peroxy radicals (BPRs) with NO were considerably lower (3–5 times) than what the current mechanism predicted. Alongside traditional ring-opening products formed through the bicyclic pathway (dicarbonyls and furanones), we identified a significant proportion of carbonyl olefinic acids generated via the 1,5-aldehydic H-shift occurring in subsequent reactions of BPRs + NO, contributing 4–7% of the carbon flow in aromatic oxidation. Moreover, the observed NOx-dependencies of ring-opening and ring-retaining product yields provide insights into the competitive nature of reactions involving BPRs with NO, HO2, and RO2, which determine the refined product distributions and offer an explanation for the discrepancies between the experimental and model-based results.
中文翻译：
深入了解芳香族光氧化的过氧化物-双环中间途径：开环和保环产物的实验产率和 NOx 依赖性
芳香烃是城市环境中臭氧和二次有机气溶胶形成的重要贡献者。然而，芳香族氧化中不同的平行途径仍然没有得到充分的了解。在这里，我们使用高分辨率质谱仪研究了大气 OH 水平下存在 NO x的烷基苯光氧化过程中气相示踪产物的产量和化学分布。过氧化物-双环中间体途径成为芳香族氧化的主要途径，分别占甲苯、间二甲苯和1,3,5的总OH氧化的52.1±12.6%、66.1±16.6%和81.4±24.3%分别为-三甲苯。值得注意的是，双环过氧自由基（BPR）与 NO 反应产生的双环硝酸盐的产率比当前机制预测的要低得多（3-5 倍）。除了通过双环途径（二羰基和呋喃酮）形成的传统开环产物外，我们还发现了很大一部分羰基烯酸是通过 BPR + NO 的后续反应中发生的 1,5-醛氢移产生的，贡献了 4-7芳族氧化中碳流量的％。此外，观察到的开环和保环产物收率的 NO x依赖性提供了对涉及 BPR 与 NO、HO 2和 RO 2的反应的竞争性质的深入了解，这决定了精炼产物的分布并为实验结果和基于模型的结果之间的差异。
更新日期：2023-11-29
中文翻译：
深入了解芳香族光氧化的过氧化物-双环中间途径：开环和保环产物的实验产率和 NOx 依赖性
芳香烃是城市环境中臭氧和二次有机气溶胶形成的重要贡献者。然而，芳香族氧化中不同的平行途径仍然没有得到充分的了解。在这里，我们使用高分辨率质谱仪研究了大气 OH 水平下存在 NO x的烷基苯光氧化过程中气相示踪产物的产量和化学分布。过氧化物-双环中间体途径成为芳香族氧化的主要途径，分别占甲苯、间二甲苯和1,3,5的总OH氧化的52.1±12.6%、66.1±16.6%和81.4±24.3%分别为-三甲苯。值得注意的是，双环过氧自由基（BPR）与 NO 反应产生的双环硝酸盐的产率比当前机制预测的要低得多（3-5 倍）。除了通过双环途径（二羰基和呋喃酮）形成的传统开环产物外，我们还发现了很大一部分羰基烯酸是通过 BPR + NO 的后续反应中发生的 1,5-醛氢移产生的，贡献了 4-7芳族氧化中碳流量的％。此外，观察到的开环和保环产物收率的 NO x依赖性提供了对涉及 BPR 与 NO、HO 2和 RO 2的反应的竞争性质的深入了解，这决定了精炼产物的分布并为实验结果和基于模型的结果之间的差异。
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