Reactive halogen species (ClO and BrO) play a critical role in the stratospheric ozone depletion. However, the reactivity of these radical moieties with volatile organic compounds is also important in determining the composition of the Earth's atmosphere. In this study, the reactions of BrO and ClO radicals with a series of smaller linear alkanes (C_nH_2n+2, n = 1,2,3, and 4) were studied using the CCSD(T)/CBS//B3LYP/cc‐pVTZ level of theory. The kinetics of the title reactions were evaluated using the Canonical Variational Transition (CVT)/Small Curvature Tunneling (SCT)/Interpolated Single Point Energy (ISPE) methodology over the studied temperature range of 200‐3000 K. H‐abstraction from the nonterminal carbon was found to be thermodynamically and kinetically favorable in comparison to abstraction of H atom from the primary carbon. On a per‐hydrogen basis at 298 K, BrO and ClO are focused to abstract the secondary hydrogens of C₃H₈ faster than the primary hydrogens by factors of 40 and 110, respectively. On the other hand, for n‐C₄H₁₀ at the same temperature, the per‐hydrogen preferences for secondary H atoms are found to be factors of 220 and 270 for BrO and ClO, respectively. To aid in modeling the stratospheric environment and combustion regime, three parameter fits to the computed rate constants between 200 and 3000 K are provided. The branching ratios and thermochemical parameters for the various reaction channels are also discussed in this paper.

中文翻译：

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一系列烷烃与ClO和BrO自由基的反应动力学：理论研究

反应性卤素物质（ClO和BrO）在平流层臭氧消耗中起关键作用。但是，这些自由基部分与挥发性有机化合物的反应性对确定地球大气的组成也很重要。在这项研究中，BrO和ClO自由基与一系列较小的直链烷烃（C _n H _{2 n + 2}，n = 1,2,3和4）是使用CCSD（T）/ CBS // B3LYP / cc-pVTZ理论水平研究的。在研究的200-3000 K的温度范围内，使用标准变分跃迁（CVT）/小曲率隧穿（SCT）/内插单点能量（ISPE）方法对标题反应的动力学进行了评估。非末端碳的H-吸收与从伯碳中提取H原子相比，发现在热力学和动力学上都具有优势。在298 K的每氢基础上，BrO和ClO的作用是使C ₃ H ₈的仲氢比伯氢更快地提取40倍和110倍。另一方面，对于n -C ₄ H ₁₀在相同温度下，发现二级氢原子的氢优先级分别是BrO和ClO的220和270。为了帮助对平流层环境和燃烧状态进行建模，提供了三个参数拟合值，该参数拟合值介于200和3000 K之间。本文还讨论了各种反应通道的支化比和热化学参数。