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Criegee Intermediate–Alcohol Reactions, A Potential Source of Functionalized Hydroperoxides in the Atmosphere
ACS Earth and Space Chemistry ( IF 3.4 ) Pub Date : 2017-12-07 00:00:00 , DOI: 10.1021/acsearthspacechem.7b00108
Max R. McGillen 1 , Basile F.E. Curchod 1 , Rabi Chhantyal-Pun 1 , Joseph M. Beames 2 , Nathan Watson 2 , M. Anwar H. Khan 1 , Laura McMahon 1 , Dudley E. Shallcross 1 , Andrew J. Orr-Ewing 1
Affiliation  

Ozonolysis, the mechanism by which alkenes are oxidized by ozone in the atmosphere, produces a diverse family of oxidants known as Criegee intermediates (CIs). Using a combination of newly acquired laboratory data and global atmospheric chemistry and transport modeling, we find that the reaction of CIs with alcohols, a reaction that was originally employed to trap these reactive species and provide evidence for the ozonolysis mechanism nearly 70 years ago, is occurring in Earth’s atmosphere and may represent a sizable source of functionalized hydroperoxides therein. Rate coefficients are reported for the reactions of CH2OO and (CH3)2COO with methanol and that of CH2OO with ethanol. Substitution about the Criegee intermediate is found to have a strong influence over the reaction rate, whereas substitution on the alcohol moiety does not. Although these reactions are not especially rapid, both the precursors to CIs and alcohols have large emissions from the terrestrial biosphere, leading to a high degree of co-location for this chemistry. We estimate that the products of these reactions, the α-alkoxyalkyl hydroperoxides (AAAHs) have a production rate of ∼30 Gg year–1. To assess the atmospheric lifetime of AAAHs, we used the nuclear ensemble method to construct a UV absorption spectrum from the four lowest energy conformers identified for a representative AAAH, methoxymethyl hydroperoxide. The computed absorption cross-section indicates that these compounds will be lost by solar photolysis, although not so rapidly as to exclude competition from other sinks such as oxidation, thermal decay, and aerosol uptake.

中文翻译:

Criegee中间醇反应,大气中功能化氢过氧化物的潜在来源

臭氧分解是烯烃在大气中被臭氧氧化的机制,它产生了多种氧化剂,称为Criegee中间体(CIs)。综合使用最新获得的实验室数据和全球大气化学及运输模型,我们发现CI与醇的反应是最初用于捕获这些反应性物种并为将近70年前的臭氧分解机制提供证据的反应。发生在地球大气中,可能代表其中相当大的功能化氢过氧化物来源。率系数被报道CH的反应2 OO和(CH 32 COO用甲醇和CH的2用乙醇OO。发现关于Criegee中间体的取代对反应速率具有强烈影响,而在醇部分上的取代则没有。尽管这些反应不是特别快,但CI和醇的前体均从陆地生物圈释放大量碳,导致该化学物质的高度共置位。我们估计,这些反应的产物,α-烷氧基氢过氧化物(啧啧)具有约30千兆克一年的生产速度-1。为了评估AAAHs的大气寿命,我们使用核能集成法从针对代表性AAAH所确定的四个最低能量构象体中建立了紫外线吸收光谱,即甲氧基甲基氢过氧化物。计算得出的吸收截面表明,这些化合物将因太阳光解而损失,尽管没有那么快地将其排除在其他吸收剂的竞争中,例如氧化,热衰减和气溶胶吸收。
更新日期:2017-12-07
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