Secondary organic aerosol formation via the isolation of individual reactive intermediates: role of alkoxy radical structure.
Secondary organic aerosol formation via the isolation of individual reactive intermediates: role of alkoxy radical structure.
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DOI：
10.1021/jp506562r
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发表时间：
2014-09
期刊：
影响因子：
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通讯作者：
A. Carrasquillo;J. F. Hunter;K. E. Daumit;J. Kroll
中科院分区：
文献类型：
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作者：
A. Carrasquillo;J. F. Hunter;K. E. Daumit;J. Kroll
化学研究的基础二次有机气溶胶（SOA）的形成是复杂的大量的反应途径和氧化代提供给一个给定的前体物种。在这里，我们简化了这样的复杂性，一个单一的烷氧基（RO），通过形成SOA通过直接光解亚硝酸烷基酯（RONO）异构体。室实验进行了11 C10 RONO异构体，以确定如何的自由基中心和分支的碳骨架的位置影响SOA的形成。SOA产率作为RO反应性的探针，较低的产率表明裂解反应占主导地位，较高的产率表明RO异构化占主导地位。产率最高的是直链异构体，特别是那些自由基中心位于朝向分子末端的异构体。SOA产率的趋势可以用两个主要影响来解释：（1）异构化和裂解反应的相对重要性，它们控制着产物的分布，以及（2）形成的各种异构体产物之间的挥发性差异。支链异构体的产率虽然较低，但变化很大，这提供了对烷氧基断裂程度的了解;在两个β-取代烷氧基的情况下，断裂程度似乎比结构-活性关系预测的更大。我们的研究结果突出了烷氧基结构的细微差异如何对产品收率和SOA形成产生重大影响。
The study of the chemistry underlying secondary organic aerosol (SOA) formation is complicated by the large number of reaction pathways and oxidation generations available to a given precursor species. Here we simplify such complexity to that of a single alkoxy radical (RO), by forming SOA via the direct photolysis of alkyl nitrite (RONO) isomers. Chamber experiments were conducted with 11 C10 RONO isomers to determine how the position of the radical center and branching of the carbon skeleton influences SOA formation. SOA yields served as a probe of RO reactivity, with lower yields indicating that fragmentation reactions dominate and higher yields suggesting the predominance of RO isomerization. The largest yields were from straight-chain isomers, particularly those with radical centers located toward the terminus of the molecule. Trends in SOA yields can be explained in terms of two major effects: (1) the relative importance of isomerization and fragmentation reactions, which control the distribution of products, and (2) differences in volatility among the various isomeric products formed. Yields from branched isomers, which were low but variable, provide insight into the degree of fragmentation of the alkoxy radicals; in the case of the two β-substituted alkoxy radicals, fragmentation appears to occur to a greater extent than predicted by structure-activity relationships. Our results highlight how subtle differences in alkoxy radical structure can have major impacts on product yields and SOA formation.