Unimolecular decay dynamics of Criegee intermediates: Energy-resolved rates, thermal rates, and their atmospheric impact
Unimolecular decay dynamics of Criegee intermediates: Energy-resolved rates, thermal rates, and their atmospheric impact
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DOI：
10.1080/0144235x.2020.1688530
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发表时间：
2020-01
影响因子：
6.1
通讯作者：
T. A. Stephenson;M. Lester
中科院分区：
文献类型：
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作者：
T. A. Stephenson;M. Lester
Criegee中间体是烯烃臭氧化反应中生成的活性物种。它们随后的化学性质对OH产生、气溶胶形成和大气氧化能力的核算至关重要。Criegee中间体在大气中的命运取决于双分子和单分子过程之间的竞争，因此了解单分子衰变是大气和物理化学中的重要课题。Criegee中间体的单分子衰变动力学对其取代基的性质和构象敏感。多种异构化途径是可能的，其中一些结构能够进行有效的1，4-氢转移反应，并且通常与双分子反应竞争。提供能量分辨速率常数（k（E））的实验研究为RRKM计算提供了基准，RRKM计算可以外推到大气条件下的热速率常数（k（T））。一系列同源Criegee中间体之间的k（E）和k（T）值的比较提供了深入了解这些物种的单分子衰变动力学中的结构，能量学和隧道效应的作用。替代单分子衰变途径也照亮了克里奇中间体的动力学方面。这些途径对隧道效应不太敏感，可能比氢转移过程更慢或更快，因此或多或少与双分子反应竞争。
ABSTRACT Criegee intermediates are reactive species formed in the ozonolysis of alkenes. Their subsequent chemistry is critical to an accounting of OH production, aerosol formation, and the oxidative capacity of the atmosphere. The fate of Criegee intermediates in the atmosphere is determined by the competition between bimolecular and unimolecular processes, so an understanding of unimolecular decay is an important topic in both atmospheric and physical chemistry. The unimolecular decay dynamics of Criegee intermediates is sensitive to the nature and conformation of its substituents. Multiple isomerisation pathways are possible, with some structures capable of a 1,4-hydrogen transfer reaction that is efficient, and generally competes with bimolecular reactions. Experimental studies that provide energy-resolved rate constants (k(E)) offer benchmarks for RRKM calculations that can be extrapolated to thermal rate constants (k(T)) under atmospheric conditions. The comparison of k(E) and k(T) values among a series of homologous Criegee intermediates provides insights into the role of structure, energetics, and tunnelling in the unimolecular decay dynamics of these species. Alternative unimolecular decay pathways also illuminate aspects of the dynamics of Criegee intermediates. These pathways are less susceptible to tunnelling, may be slower or faster than hydrogen transfer processes, and thus more or less competitive with bimolecular reactions.