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首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >Highly Oxidized Second-Generation Products from the Gas-Phase Reaction of OH Radicals with Isoprene
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Highly Oxidized Second-Generation Products from the Gas-Phase Reaction of OH Radicals with Isoprene

机译：OH自由基与异戊二烯的气相反应产生的高度氧化的第二代产物

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The gas-phase reaction of OH radicals with isoprene has been investigated in an atmospheric pressure flow tube at 293 +/- 0.5 K with special attention to the second-generation products. Reaction conditions were optimized to achieve a predominant reaction of RO2 radicals with HO2 radicals. Chemical ionization-atmospheric pressure interface time-of-flight mass spectrometry served as the analytical technique in order to follow the formation of RO2 radicals and closed-shell products containing at least four O atoms. in the molecule. The reaction products were detected as adducts with the reagent ions using acetate, lactate, or nitrate in the ionization process. Observed signals were attributed to a series of C-5-products with multiple hydroxy, hydroperoxy, and probably carbonyl groups. H/D exchange experiments supported the product identification. The generation of the detected second-generation products can be mechanistically explained starting from the OH radical reaction of hydroxy hydroperoxide isomers, HO-O5H8-OOH. These isomers represent the dominant products of the initial OH radical attack on isoprene. Dihydroxy dihydroperoxides, (HO)(2)-O5H8-(OOH)(2), were analyzed as the main second-generation products beside the dihydroxy epoxides. A simple kinetic analysis revealed that the observed second-generation products in total (other than dihydroxy epoxides) were formed with an estimated molar yield of 10.0(-1.5)(+2.1) % with respect to converted hydroxy hydroperoxides. A formation yield of 5.8(-0.9)(+1.3) % has been deduced for the main product (HO)(2)-O5H8-(OOH)(2). The detected, highly oxidized isoprene products represent potential secondary organic aerosol precursors. An annual, global (HO)(2)-O5H8-(OOH)(2) formation strength of (16-35) x 10(6) metric tons is estimated based on product measurements of this study and literature data regarding the formation of the dihydroxy epoxide isomers for an annual isoprene emission of 454 x 10(6) metric tons of carbon.
机译：OH自由基与异戊二烯的气相反应已在293 +/- 0.5 K的大气压流管中进行了研究，特别注意第二代产品。优化反应条件以实现RO 2自由基与HO 2自由基的主要反应。化学电离-大气压界面飞行时间质谱是一种分析技术，目的是跟踪RO2自由基和至少包含四个O原子的闭壳产物的形成。在分子中。在电离过程中，使用乙酸盐，乳酸盐或硝酸盐将反应产物与试剂离子检测为加合物。观察到的信号归因于一系列具有多个羟基，氢过氧基以及可能还有羰基的C-5-产物。 H / D交换实验支持产品识别。可以从羟基氢过氧化物异构体HO-O5H8-OOH的OH自由基反应开始，从机械上解释检测到的第二代产物的产生。这些异构体代表初始OH自由基攻击异戊二烯的主要产物。二羟基二氢过氧化物（HO）（2）-O5H8-（OOH）（2）被分析为除二羟基环氧化物外的主要第二代产物。简单的动力学分析表明，形成的总观察到的第二代产物（除二羟基环氧化物外）相对于转化的羟基氢过氧化物的估计摩尔产率为10.0（-1.5）（+ 2.1）％。对于主产物（HO）（2）-O5H8-（OOH）（2），推断出的形成产率为5.8（-0.9）（+ 1.3）％。检测到的高度氧化的异戊二烯产品代表潜在的次级有机气溶胶前体。根据本研究的产品测量结果和有关形成的文献数据，估计年度（HO）（2）-O5H8-（OOH）（2）的形成强度为（16-35）x 10（6）公吨。二羟基环氧化物异构体，每年异戊二烯排放量为454 x 10（6）公吨碳。

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