Quantum chemical calculations were used to investigate the mechanism and kinetics of the reaction of XO (X = Cl, Br) radicals with linear C₂ to C₄ alkenes. Two reaction routes, namely, addition and H‐abstraction, were investigated as part of the XO‐radical initiated degradation of these alkenes. Energies and structural parameters were obtained at the CCSD(T)/CBS//M062x/cc‐pVTZ level of theory, and the canonical variational transition state theory with small‐curvature tunneling corrections was used to calculate rate constants at temperatures spanning 200‐3000 K. The addition of the electron‐deficient XO radical onto the olefinic moiety was the major degradation channel, owing to its low barrier heights. Moreover, the H‐abstraction route also played a key role in governing the fate of the alkene in the high‐temperature regime, when compared to the addition routes. The computed branching ratios for various reaction routes further ascertained the relative dominance of the addition and H‐abstraction routes over the studied temperature range. The computed kinetic and thermodynamic parameters can be beneficial towards designing a better chemical kinetic model, relevant for both atmospheric as well as combustion systems. In addition to this, the formed HOCl (or HOBr) can damage the ozone layer and cause ecological imbalance.

中文翻译：

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一系列烯烃与ClO和BrO自由基的反应动力学：理论研究

使用量子化学计算研究XO（X = Cl，Br）自由基与线性C ₂至C ₄反应的机理和动力学烯烃。作为XO自由基引发这些烯烃降解的一部分，研究了两种反应途径，即加成反应和H-抽象反应。在CCSD（T）/ CBS // M062x / cc-pVTZ的理论水平上获得了能量和结构参数，并使用具有小曲率隧道校正的规范变分过渡状态理论来计算温度跨度200-3000时的速率常数K.由于其低势垒高度，将缺电子的XO自由基加到烯烃部分是主要的降解通道。此外，与加成路线相比，H吸收路线在控制高温状态下烯烃的命运方面也起着关键作用。计算出的各种反应路线的支化比进一步确定了在研究温度范围内加成和H-吸收路线的相对优势。计算出的动力学和热力学参数可能有助于设计一个更好的化学动力学模型，该模型对于大气系统和燃烧系统都至关重要。除此之外，所形成的HOCl（或HOBr）会破坏臭氧层并引起生态失衡。