A comprehensive study on the reaction of H + C₃H₆ has been conducted in order to clarify the temperature and pressure dependence of product branching. Site‐specific rate of addition of a hydrogen atom to the center carbon is measured by a comparative method for the evolutions of H atoms behind reflected shock waves. The rate constant for the addition to the center carbon can be given by ln(k_1‐2/cm³molecule^–1s^–1) = – (1.67 ± 0.65) × 10³ T^–1 – (24.18 ± 0.55) for H + C₃H₆ → n‐C₃H₇^* → products (T = 1065‐1306 K) without pressure dependence for P = 1‐2 bar. Theoretical calculation was conducted to evaluate the pressure dependence of the product branching for the H + C₃H₆ reaction by using transition‐state theory and RRKM theory based on quantum‐chemical calculations of potential‐energy surfaces. The result indicates that transition of the main reaction channel from addition to the terminal carbon in the low temperature range to the central carbon at moderate pressures (0.001‐10 bar) and elevated temperatures causes S‐shaped non‐Arrhenius temperature dependence of the total reaction rate against T^–1; at the transition temperature, a strong pressure dependence was predicted. Our experimental result of k_1‐2 agrees very well with the predicted value and available experimental data. The predicted rate constant ratio for the terminal versus nonterminal additions at the high‐pressure limits agrees well with the temperature dependence reported by Manion and Awan for the analogous H + C₄H₈ reaction. Furthermore, the importance of H‐abstraction reactions at elevated temperatures from three different sites of C₃H₆ was predicted in this calculation. For kinetic modeling of combustion and pyrolysis of hydrocarbons, we have recommended the rate constants for the 3 abstraction reactions as well as for the production of i‐ and n‐C₃H₇ radicals by addition reactions at the high‐ and low‐pressure limits over the temperature range of 300‐2000 K.

中文翻译：

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H原子与C3H6反应的实验和理论研究

为了阐明产物支化的温度和压力依赖性，已经对H + C ₃ H ₆的反应进行了全面研究。氢原子向中心碳加成的特定位置速率是通过一种比较方法测量的，该方法用于分析反射冲击波背后的H原子。中心碳的添加速率常数可以通过以下公式给出：ln（k ₁₋₂ / cm ³分子^–1 s ^–1）= –（1.67±0.65）×10 ³  T ^–1  –（24.18±0.55） H + C ₃ H ₆  →n‐C ₃ H ₇ ^*  →产品（T = 1065-1306 K），且压力无关，P  = 1-2 bar。利用过渡态理论和RRKM理论，基于势能面的量子化学计算，对H + C ₃ H ₆反应的产物支链的压力依赖性进行了理论计算。结果表明，在中等压力（0.001-10 bar）和升高的温度下，主要反应通道从低温范围内的末端碳过渡到中心碳的过渡导致整个反应的S形非阿累尼乌斯温度依赖性相对于T ^–1的速率；在转变温度下，预测到很强的压力依赖性。我们的实验结果ķ_1-2非常符合预测值和可用的实验数据。在高压极限下，末端和非末端加料的预测速率常数比与Manion和Awan报告的类似的H + C ₄ H ₈反应的温度依赖性非常吻合。此外，在此计算中还预测了在三个不同位置的C ₃ H ₆升高的温度下H吸收反应的重要性。对于烃类燃烧和热解的动力学模型，我们建议了3种抽象反应以及i-和n-C ₃ H ₇生成的速率常数。 在300-2000 K的温度范围内在高压和低压极限下通过加成反应产生的自由基。