Thermodynamics of the hydroxyl radical addition to isoprene.
Thermodynamics of the hydroxyl radical addition to isoprene.
复制标题
羟基自由基加成异戊二烯的热力学。
DOI：
10.1021/jp801869c
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发表时间：
2008
期刊：
影响因子：
--
通讯作者：
Shields,GeorgeC
中科院分区：
文献类型：
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作者：
Allodi,MarcoA;Kirschner,KarlN;Shields,GeorgeC
异戊二烯被羟基自由基氧化导致对流层臭氧的形成。因此，更全面地了解这种反应可以导致更好的区域空气质量模型，更好地了解气溶胶的形成，更好地了解反应动力学和动力学。异戊二烯氧化的最常见的第一步是形成加合物，其中羟基加到异戊二烯中的四个不饱和碳原子之一上。在本文中，我们讨论了异戊二烯的初始构象，S-反式-gauche，影响加合物形成的途径。我们探讨了在低温和高温下预反应复合物的形成，这通常被用来解释该反应动力学的负温度依赖性。我们表明，在较高的温度下的自由能表面表明，预反应复合物是不可能的，而在低温下的复杂存在于两个反应途径。理论结果表明，在低温下，所有八种途径都具有负反应势垒，反应能量范围为−36.7至−23.0 kcal·mol−1。在低层大气温度下，所有八条路径都具有正反应势垒，范围为3.8至6.0 kcal·mol− 1，反应能量范围为−28.8至−14.4 kcal·mol−1。
Oxidation of isoprene by the hydroxyl radical leads to tropospheric ozone formation. Consequently, a more complete understanding of this reaction could lead to better models of regional air quality, a better understanding of aerosol formation, and a better understanding of reaction kinetics and dynamics. The most common first step in the oxidation of isoprene is the formation of an adduct, with the hydroxyl radical adding to one of four unsaturated carbon atoms in isoprene. In this paper, we discuss how the initial conformations of isoprene,s-transands-gauche, influences the pathways to adduct formation. We explore the formation of pre-reactive complexes at low and high temperatures, which are often invoked to explain the negative temperature dependence of this reaction’s kinetics. We show that at higher temperatures the free energy surface indicates that a pre-reactive complex is unlikely, while at low temperatures the complex exists on two reaction pathways. The theoretical results show that at low temperatures all eight pathways possess negative reaction barriers, and reaction energies that range from −36.7 to −23.0 kcal·mol−1. At temperatures in the lower atmosphere, all eight pathways possess positive reaction barriers that range from 3.8 to 6.0 kcal·mol−1and reaction energies that range from −28.8 to −14.4 kcal·mol−1.