Laboratory studies of the hydrogen kinetic isotope effects (KIES) of the reaction of non-methane hydrocarbons with the OH radical in the gas phase
Laboratory studies of the hydrogen kinetic isotope effects (KIES) of the reaction of non-methane hydrocarbons with the OH radical in the gas phase
复制标题
DOI：
10.1023/b:joch.0000021035.49613.f7
复制
发表时间：
2004-02-01
影响因子：
2
通讯作者：
Whiticar, MJ
中科院分区：
文献类型：
--
作者：
Iannone, R;Anderson, RS;Whiticar, MJ
在298 +/-2K下，测定了15种非甲烷烃（NMHCs）与OH自由基反应的氢动力学同位素效应（KIE）。使用NMHC进行测量，而不进行人工同位素标记或富集。以下平均氢KIE值（单位：每密耳）（千分之几），得到：29.8 +/- 2.1（甲苯），51.6 +/- 2.1（正丁烷），97.3 +/- 12.5（异丁烷），63.2 +/- 5.9（环戊烷），10.5（对二甲苯），26.8 +/- 3.5（），65.9 +/- 7.0（正戊烷），79.5 +/- 9.6（环己烷）、52.8 +/- 5.0（正己烷）、38.9 +/- 7.8（正庚烷）、33.4 +/- 3.1（正辛烷）、29.6 +/- 1.6（正壬烷）和29.0 +/- 5.3（正癸烷）。两种烯烃（环己烯和1-庚烯）的反应的KIE不能准确地确定，由于与臭氧反应的干扰，但结果清楚地表明，烯烃与OH的反应的KIE显着低于饱和烃。烷烃反应的KIE小于文献报道的人工标记氘的NMHCs反应的同位素效应。这种差异的主要原因是在接近天然氘丰度的化合物的标记位点反应的可能性降低，尽管不能排除次级同位素效应的一些影响。尽管如此，具有天然或接近天然氘丰度的非金属碳氢化合物的KIE具有足够的量级，允许使用类似于稳定碳KIE研究的方法来确定大气中碳氢化合物的化学加工程度。此外，它表明，结合稳定的氢和稳定的碳同位素比的数据也有可能提供有价值的信息，关于排放的稳定同位素比，特别是测试的稳定同位素碳氢化合物时钟的关键假设之一，没有显着变化的稳定同位素比的排放NMHCs。
The hydrogen kinetic isotope effects (KIEs) of the reactions of 15 non-methane hydrocarbons (NMHCs) with the OH radical were measured at 298 +/- 2 K. The measurements were made using NMHCs without artificial isotopic labeling or enrichment. The following average hydrogen KIE values, in per mil (parts per thousand), were obtained: 29.8 +/- 2.1 (toluene), 51.6 +/- 2.1 (n-butane), 97.3 +/- 12.5 (i-butane), 63.2 +/- 5.9 (cyclopentane), 10.5 (p-xylene), 26.8 +/- 3.5 (ethylbenzene), 65.9 +/- 7.0 (n-pentane), 79.5 +/- 9.6 (cyclohexane), 52.8 +/- 5.0 (n-hexane), 38.9 +/- 7.8 (n-heptane), 33.4 +/- 3.1 (n-octane), 29.6 +/- 1.6 (n-nonane), and 29.0 +/- 5.3 (n-decane). The KIEs for reactions of two alkenes ( cyclohexene and 1-heptene) could not be determined accurately due to interference from reaction with ozone, but nevertheless the results clearly show that the KIEs for reaction of alkenes with OH are significantly lower than those for saturated hydrocarbons. The KIEs for reaction of alkanes are smaller than isotope effects reported in literature for the reactions of NMHCs artificially labeled with deuterium. The main reason for this difference is the reduced probability for reaction at a labeled site for compounds with close to natural deuterium abundance, although some impact of secondary isotope effects cannot be ruled out. Still, the KIEs for NMHCs with natural or close to natural abundance of deuterium are of sufficient magnitude to allow determination of the extent of chemical processing of hydrocarbons in the atmosphere using methods analogous to stable carbon KIE studies. Furthermore, it is shown that combining stable hydrogen and stable carbon isotope ratio data has the potential to also provide valuable information regarding the stable isotope ratios of emissions, and specifically to test one of the key assumptions of the stable isotope hydrocarbon clock, the absence of significant variations of the stable isotope ratio for the emitted NMHCs.