Barrierless bond dissociation reactions play an important role in fuel combustion. In this work, the pressure-dependent dissociation rate constants of ethylamine (EA) are accurately determined using variable-reaction-coordinate variational transition-state theory combined with the system-specific quantum Rice–Ramsperger–Kassel method. Before the kinetics calculations, the performances of four density functional theory methods in describing the bond dissociation of EA are evaluated against the benchmark method, FIC-MRCISD(T)+Q/cc-pVTZ, and the MN15-L/cc-pVTZ method is the best choice. By comparison of the Gibbs free energies and the rate constants for the bond dissociation reactions of EA, ethanol, and propane, the influence of functional groups on the reaction kinetics is discussed. The kinetics calculations show that the dissociation rate constants of EA are sensitive to pressure at low pressures and high temperatures, and the dominant channel is the reaction that yields C₂H₅ and NH₂ radicals. A literature combustion model of EA is updated with our calculations, and the satisfactory agreement between the model predictions and reported ignition delay times of EA suggests the reliability of our calculations.

中文翻译：

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使用 VRC-VTST 和 SS-QRRK 方法进行乙胺解离反应的理论研究

无势垒键解离反应在燃料燃烧中发挥着重要作用。在这项工作中，利用可变反应配位变分过渡态理论结合系统特定的量子Rice-Ramsperger-Kassel方法准确测定了乙胺（EA）的压力依赖性解离速率常数。在动力学计算之前，根据基准方法 FIC​​-MRCISD(T)+Q/cc-pVTZ 和 MN15-L/cc-pVTZ 方法评估了四种密度泛函理论方法在描述 EA 键解离方面的性能是最好的选择。通过比较EA、乙醇和丙烷键解离反应的吉布斯自由能和速率常数，讨论了官能团对反应动力学的影响。动力学计算表明，在低压和高温下，EA的解离速率常数对压力敏感，主要通道是产生C ₂ H ₅和NH ₂自由基的反应。我们的计算更新了 EA 的文献燃烧模型，并且模型预测和报告的 EA 点火延迟时间之间的令人满意的一致性表明我们计算的可靠性。