Observation of a new channel, the production of CH3, in the abstraction reaction of OH radicals with acetaldehyde.
Observation of a new channel, the production of CH3, in the abstraction reaction of OH radicals with acetaldehyde.
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DOI：
10.1039/c6cp03970g
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发表时间：
2016-09
期刊：
影响因子：
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通讯作者：
Neil U. M. Howes;J. Lockhart;M. Blitz;Scott A. Carr;M. Baeza_Romero;D. Heard;R. Shannon;P. Seakins;T. Varga
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文献类型：
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作者：
Neil U. M. Howes;J. Lockhart;M. Blitz;Scott A. Carr;M. Baeza_Romero;D. Heard;R. Shannon;P. Seakins;T. Varga
利用激光闪光光解耦合光电离飞行时间质谱（PIMS），甲基自由基（CH 3）已被检测为初级产物的OH自由基与乙醛（乙醛，CH 3 CHO）的反应，在1-2托的氦浴气体的产率约15%。基于OH/CH 3CHO/O2系统中OH再循环的激光诱导荧光研究的支持测量与PIMS研究一致。主方程计算表明，甲基自由基的起源是从化学活化的乙酰基产品的迅速解离，因此与先前的研究表明，抽象，而不是添加/消除，是OH +乙醛反应的唯一途径是一致的。然而，一个显着的甲基产物产率的观察表明，在反应中的能量分配是不同的典型的早期势垒机制，其中反应介电性被引导优先进入新形成的键。主方程计算预测大气中甲基自由基的产率为0.9%。在大气和燃烧化学的意见的影响进行了简要讨论。
Using laser flash photolysis coupled to photo-ionization time-of-flight mass spectrometry (PIMS), methyl radicals (CH3) have been detected as primary products from the reaction of OH radicals with acetaldehyde (ethanal, CH3CHO) with a yield of ∼15% at 1-2 Torr of helium bath gas. Supporting measurements based on laser induced fluorescence studies of OH recycling in the OH/CH3CHO/O2 system are consistent with the PIMS study. Master equation calculations suggest that the origin of the methyl radicals is from prompt dissociation of chemically activated acetyl products and hence is consistent with previous studies which have shown that abstraction, rather than addition/elimination, is the sole route for the OH + acetaldehyde reaction. However, the observation of a significant methyl product yield suggests that energy partitioning in the reaction is different from the typical early barrier mechanism where reaction exothermicity is channeled preferentially into the newly formed bond. The master equation calculations predict atmospheric yields of methyl radicals of ∼9%. The implications of the observations in atmospheric and combustion chemistry are briefly discussed.