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首页> 外文OA文献 >Complex chemical composition of colored surface films formed from reactions of propanal in sulfuric acid at upper troposphere/lower stratosphere aerosol acidities
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Complex chemical composition of colored surface films formed from reactions of propanal in sulfuric acid at upper troposphere/lower stratosphere aerosol acidities

机译：对流层上层/平流层下层气溶胶酸度由丙酸在硫酸中的反应形成的彩色表面膜的复杂化学组成

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Particles in the upper troposphere and lower stratosphere (UT/LS) consistmostly of concentrated sulfuric acid (40–80 wt%) in water. However,airborne measurements have shown that these particles also contain asignificant fraction of organic compounds of unknown chemical composition.Acid-catalyzed reactions of carbonyl species are believed to be responsiblefor significant transfer of gas phase organic species into troposphericaerosols and are potentially more important at the high aciditiescharacteristic of UT/LS particles. In this study, experiments combiningsulfuric acid (HSO) with propanal and with mixtures of propanalwith glyoxal and/or methylglyoxal at acidities typical of UT/LS aerosolsproduced highly colored surface films (and solutions) that may haveimplications for aerosol properties. In order to identify the chemicalprocesses responsible for the formation of the surface films, attenuatedtotal reflectance–Fourier transform infrared (ATR-FTIR) and H nuclear magneticresonance (NMR) spectroscopies were used to analyze the chemical composition of thefilms. Films formed from propanal were a complex mixture of aldolcondensation products, acetals and propanal itself. The major aldolcondensation products were the dimer (2-methyl-2-pentenal) and1,3,5-trimethylbenzene that was formed by cyclization of the linear aldolcondensation trimer. Additionally, the strong visible absorption of the filmsindicates that higher-order aldol condensation products must also be presentas minor species. The major acetal species were2,4,6-triethyl-1,3,5-trioxaneand longer-chain linear polyacetals which are likely to separate from theaqueous phase. Films formed on mixtures of propanal with glyoxal and/ormethylglyoxal also showed evidence of products of cross-reactions. Sincecross-reactions would be more likely than self-reactions under atmosphericconditions, similar reactions of aldehydes like propanal with common aerosolorganic species like glyoxal and methylglyoxal have the potential to producesignificant organic aerosol mass and therefore could potentially impactchemical, optical and/or cloud-forming properties of aerosols, especially ifthe products partition to the aerosol surface.
机译：对流层和平流层下部（UT / LS）中的颗粒主要由水中的浓硫酸（40-80 wt％）组成。然而，空中测量结果表明，这些颗粒中还含有相当一部分化学成分未知的有机化合物。羰基物质的酸催化反应被认为是导致气相有机物向对流层气溶胶大量转移的原因，并且在高温下可能更重要。 UT / LS颗粒的酸度特性。在这项研究中，在UT / LS气溶胶的典型酸性下，将硫酸（HSO）与丙醛以及丙醛与乙二醛和/或甲基乙二醛的混合物结合使用的实验产生了高度着色的表面膜（和溶液），这可能对气溶胶特性有影响。为了确定造成表面膜形成的化学过程，使用衰减全反射傅里叶红外光谱（ATR-FTIR）和H核磁共振（NMR）光谱仪分析了膜的化学成分。由丙醛形成的薄膜是醛醇缩合产物，乙缩醛和丙醛本身的复杂混合物。主要的醛醇缩合产物是通过线性醛醇缩合三聚体的环化反应而形成的二聚物（2-甲基-2-戊烯）和1,3,5-三甲基苯。此外，薄膜强烈的可见光吸收表明，高级醛醇缩合产物也必须作为次要物质存在。乙缩醛的主要种类是2,4,6-三乙基-1,3,5-三恶烷和长链线性聚缩醛，它们很可能与水相分离。在丙醛与乙二醛和/或甲基乙二醛的混合物上形成的膜也显示出交叉反应产物的证据。由于在大气条件下交叉反应比自反应更可能发生，因此醛类（如丙醛）与常见的气溶胶有机物（如乙二醛和甲基乙二醛）的类似反应有可能产生大量的有机气溶胶，因此有可能影响化学，光学和/或云形成特性的气溶胶，特别是如果产品分配到气溶胶表面。

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