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首页> 外文期刊>Atmospheric Chemistry and Physics Discussions >Ozonolysis of surface-adsorbed methoxyphenols: kinetics of aromatic ring cleavage vs. alkene side-chain oxidation
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Ozonolysis of surface-adsorbed methoxyphenols: kinetics of aromatic ring cleavage vs. alkene side-chain oxidation

机译：表面吸附的甲氧基苯酚的臭氧分解：芳环裂解与烯烃侧链氧化的动力学

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pstrongAbstract./strong Lignin pyrolysis products, which include a variety of substituted methoxyphenols, constitute a major component of organics released by biomass combustion, and may play a central role in the formation of atmospheric brown carbon. Understanding the atmospheric fate of these compounds upon exposure to trace gases is therefore critical to predicting the chemical and physical properties of biomass burning aerosol. We used diffuse reflectance infrared spectroscopy to monitor the heterogeneous ozonolysis of 4-propylguaiacol, eugenol, and isoeugenol adsorbed on NaCl and ?±-Alsub2/subOsub3/sub substrates. Adsorption of gaseous methoxyphenols onto these substrates produced near-monolayer surface concentrations of 3 ?? 10sup18/sup molecules msupa??2/sup. The subsequent dark heterogeneous ozonolysis of adsorbed 4-propylguaiacol cleaved the aromatic ring between the methoxy and phenol groups with the product conclusively identified by GC-MS and sup1/supH-NMR. Kinetic analysis of eugenol and isoeugenol dark ozonolysis also suggested the formation of ring-cleaved products, although ozonolysis of the unsaturated substituent groups forming carboxylic acids and aldehydes was an order of magnitude faster. Average uptake coefficients for NaCl-adsorbed methoxyphenols were ?3 = 2.3 (?± 0.8) ?? 10sup−7/sup and 2 (?± 1) ?? 10sup−6/sup for ozonolysis of the aromatic ring and the unsaturated side chain, respectively, and reactions on ?±-Alsub2/subOsub3/sub were approximately two times slower. UVa??visible radiation (?? 300 nm) enhanced eugenol ozonolysis of the aromatic ring by a factor of 4(?± 1) but had no effect on ozonolysis of the alkene side chain./p.
机译：> >摘要。木质素热解产物包括多种取代的甲氧基酚，它们构成了生物质燃烧释放的有机物的主要成分，并可能在大气棕碳的形成中发挥重要作用。因此，了解这些化合物暴露于痕量气体后的大气命运对于预测燃烧生物质的气溶胶的化学和物理性质至关重要。我们使用漫反射红外光谱法监测了在NaCl和α±-Al 2 O 3 基质上吸附的4-丙基愈创木酚，丁子香酚和异丁香酚的异质臭氧分解。气态甲氧基苯酚在这些基质上的吸附使单层表面浓度接近3 ??。 10 18 个分子m a ?? 2 。随后被吸附的4-丙基愈创木酚的深色多相臭氧分解将甲氧基和酚基之间的芳环裂解，产物通过GC-MS和 1 H-NMR最终鉴定。丁香酚和异丁香酚的暗臭氧分解动力学分析也表明形成了环裂解产物，尽管形成羧酸和醛的不饱和取代基的臭氧分解速度快了一个数量级。 NaCl吸附的甲氧基苯酚的平均吸收系数为？3 = 2.3（？±0.8）？ 10 ＆minus; 7 和2（？±1）?? 10 ＆minus; 6 分别用于芳香环和不饱和侧链的臭氧分解，并且在α±-Al 2 O 3 上发生反应慢大约两倍。 UVa？可见辐射（Δε> 300 nm）可将丁香酚对丁香酚的臭氧分解作用提高4（？±1），但对烯烃侧链的臭氧分解没有影响。。

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