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首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >Ab Initio Study of Radical Reactions: Cyelization Pathways for the Butylbenzene Radical (II)
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Ab Initio Study of Radical Reactions: Cyelization Pathways for the Butylbenzene Radical (II)

机译：自由基反应的从头算研究：丁基苯自由基的塞尔化路径（II）

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摘要

Ab initio density functional theory calculations are presented on some model reactions involved in coke formation during the thermal cracking of hydrocarbons. The reactions under consideration are different cyclization pathways for the butylbenzene radical, which can lead to a further growth of the coke layer. This study enables us to gain more microscopic insight into the mechanistic and kinetic aspects of the reactions. Special attention is paid to the exact treatment of internal rotations and their impact on the kinetic parameters. Pre-exponential factors are very sensitive to the accuracy of constructing the microscopic partition functions. In particular, the relative importance of cyclization toward five and six-membered rings is studied on the basis of the calculated rate constants and concentration profiles of the reactants. The influence of the size of the ring and of the relative stability of the primary and secondary butylbenzene radical on the cyclization reaction is discussed. The activation energy for the formation of six-membered rings is approximately 30 kJ/mol lower than that for five-ring formation. The predicted values for the kinetic parameters enable us to validate some basic assumptions on coke formation. The calculations as presented here are especially important for complex reaction schemes, for which experimental data are not always available.
机译：从头算密度泛函理论计算给出了碳氢化合物热裂解过程中焦炭形成过程中涉及的一些模型反应。所考虑的反应是丁苯自由基的不同环化途径，这可能导致焦炭层的进一步增长。这项研究使我们能够更深入地了解反应的机理和动力学方面。特别注意内旋的精确处理及其对动力学参数的影响。预指数因子对构造微观分区函数的准确性非常敏感。尤其是，基于计算出的速率常数和反应物的浓度分布图，研究了环向五元环和六元环的相对重要性。讨论了环的大小以及伯丁基和仲丁基苯自由基的相对稳定性对环化反应的影响。形成六元环的活化能比形成五环的活化能低约30 kJ / mol。动力学参数的预测值使我们能够验证关于焦炭形成的一些基本假设。对于复杂的反应方案而言，此处介绍的计算尤其重要，因为对于这些方案而言，实验数据并非始终可用。

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