A new look at reactions of 2-butoxy and 1-butoxy radicals in the presence of oxygen.
A new look at reactions of 2-butoxy and 1-butoxy radicals in the presence of oxygen.
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氧气存在下 2-丁氧基和 1-丁氧基自由基反应的新视角。
DOI：
10.1039/b806591h
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发表时间：
2008
期刊：
影响因子：
--
通讯作者：
A. Bergeat
中科院分区：
文献类型：
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作者：
F. Caralp;W. Forst;A. Bergeat
在大气条件下，实验表明，2-丁氧基自由基在氧的存在下产生乙醛和丁酮，使得[乙醛] [O2]/[丁酮]的浓度比显示出对氧浓度[O2]的线性依赖性。[Zabel等人，物理化学物理，2002，4，2579;考克斯（Cox）等人，物理化学（Phys. Chem. Chem. Phys），2005，7，3702。]考克斯等人在1-丁氧基自由基的反应中发现了类似的氧依赖性。这些实验暗示了单分子速率常数显然取决于氧压。以前，这已经解释了假设存在少量的激发自由基假定进行“提示”解离。我们提出了一个替代的解释的基础上的时间依赖性的主方程的解决方案，不需要假定存在的激发自由基。我们这样做，让时间运行，直到所谓的长时间稳定状态，然后表明，氧的依赖性出现很自然，如果运输矩阵考虑到，除了主要的反应通道（在2-丁氧基的情况下分解成乙醛，在1-丁氧基的情况下异构化），由于与氧的反应而存在烷氧基的少量“泄漏”，并且假设计算考虑到在所引用的实验中存在丁氧基自由基的连续进入流。
Under atmospheric conditions, experiments show that 2-butoxy radicals in the presence of oxygen yield acetaldehyde and butanone such that the concentration ratio [acetaldehyde] [O2]/[butanone] shows a linear dependence on oxygen concentration [O2]. [Zabel et al., Phys. Chem. Chem. Phys., 2002, 4, 2579; Cox et al.Phys. Chem. Chem. Phys, 2005, 7, 3702.] A similar oxygen dependence was found by Cox et al. in the reactions of 1-butoxy radicals. These experiments imply a unimolecular rate constant that apparently depends on oxygen pressure. Previously this has been explained by postulating the presence of a small amount of excited radicals assumed to undergo 'prompt' dissociation. We propose an alternative interpretation based on the solution of the time-dependent master equation that does not require the putative presence of excited radicals. We do this by allowing the time to run until the so-called long-time steady-state, and then show that the oxygen dependence arises quite naturally if the transport matrix takes into account that in addition to the principal reaction channel (dissociation into acetaldehyde in the case of 2-butoxy and isomerization in the case of 1-butoxy), there is a small "leak" of alkoxy radicals due to the reaction with oxygen, and provided the calculation takes into account that in the cited experiments there is a continuous incoming flux of butoxy radicals.