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首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >Barriers of Hydrogen Abstraction from Primary, Secondary, and Tertiary Alkane Sites by 0(3P)
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Barriers of Hydrogen Abstraction from Primary, Secondary, and Tertiary Alkane Sites by 0(3P)

机译：0（3P）从一级，二级和三级烷烃站点提取氢的障碍

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We present an extensive study of the barriers of hydrogen abstraction from primary, secondary, and tertiary sites of acyclic alkanes by ground-state oxygen atoms. Our studies include the characterization of the lowest-energy transition states of the 0(3P) reactions with methane, ethane, propane, isobutane, and isopentane using high-level ab initio methods. The order of the calculated barriers heights is primary > secondary > tertiary, in agreement with the trends gleaned from kinetic measurements. Analysis of the transition-state geometry reveals a shift toward more reagents-like structures in the primary -> secondary -> tertiary sequence, which concurs with the expectation from Hammond's postulate. Using the ab initio data, we calculate thermal rate constants via transition-state theory. Our highest-level calculations indicate that the room-temperature relative reactivities of primary, secondary, and tertiary alkane sites in hydrogen-abstraction reactions by ground-state oxygen atoms are 1, 29, and 422, respectively. These results are used to interpret recent experiments on the reactions of 0(3P) with liquid alkanes.
机译：我们对基态氧原子从无环烷烃的伯，仲和叔位提取氢的障碍进行了广泛的研究。我们的研究包括使用高级从头算方法表征与甲烷，乙烷，丙烷，异丁烷和异戊烷的0（3P）反应的最低能量跃迁状态。计算出的势垒高度的顺序是初级>次级>三级，与动力学测量得出的趋势一致。对过渡态几何结构的分析表明，在一级->二级->三级序列中，向着更多试剂样结构的转变，这与哈蒙德的假设相符。使用从头算数据，我们通过过渡态理论计算热速率常数。我们的最高水平计算表明，基态氧原子在吸氢反应中伯，仲和叔烷烃位点的室温相对反应性分别为1、29和422。这些结果用于解释0（3P）与液态烷烃反应的最新实验。

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