Formation and Oxidation of Imidazole in Tropospheric Aqueous-Phase Chemistry: A Computational Study

ACS ES&T Air Pub Date : 2024-05-09 DOI:10.1021/acsestair.3c00097

Bo Wei, Ruifeng Zhang, Patrick H.-L. Sit*, Maoxia He and Chak K. Chan*,

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Abstract

Imidazole produced by the interaction of glyoxal with nitrogen-containing chemicals in atmospheric particles can yield secondary organic aerosol (SOA) due to atmospheric oxidation. However, knowledge about the aqueous phase reaction mechanism of imidazole formation and its oxidation is still very limited. This work investigated the formation mechanism and aqueous-phase oxidative degradation reactions of imidazole with the hydroxyl radical (^•OH), nitrate radical (NO₃^•), and ozone (O₃). Results showed that the formation of imidazole involves many dehydration reactions and is favorable under moderate- or low-RH conditions. The calculated atmospheric lifetimes of 14.05, 0.27, and 3.45 h for reactions with ^•OH, NO₃^•, and O₃, respectively, suggest the efficient oxidation of imidazole under tropospheric aqueous-phase conditions. Formamide and oxamide are the main products in the presence of O₂, and nitro-imidazoles can also be formed in the presence of NO₂. The optical properties of imidazole evolve significantly, attributable to the formation of nitro-imidazoles, resulting in a red shift of absorption peak to the UVA and UVB region.

Formamide and oxamide are the main aqueous oxidation products of imidazole, implying a potentially important source of SOA.

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对流层水相化学中咪唑的形成和氧化：计算研究

乙二醛与大气颗粒中的含氮化学物质相互作用产生的咪唑会在大气氧化作用下生成二次有机气溶胶（SOA）。然而，有关咪唑形成及其氧化的水相反应机制的知识仍然非常有限。这项工作研究了咪唑与羟基自由基（-OH）、硝酸自由基（NO3-）和臭氧（O3）的形成机理和水相氧化降解反应。结果表明，咪唑的形成涉及许多脱水反应，在中度或低度相对湿度条件下有利。计算得出的与 -OH、NO3- 和 O3 反应的大气寿命分别为 14.05、0.27 和 3.45 小时，这表明在对流层水相条件下咪唑的氧化效率很高。甲酰胺和草酰胺是 O2 存在下的主要产物，硝基咪唑也可在 NO2 存在下生成。由于形成了硝基咪唑，咪唑的光学特性发生了显著变化，导致吸收峰向 UVA 和 UVB 区域红移。

本文章由计算机程序翻译，如有差异，请以英文原文为准。

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