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Criegee intermediate-alcohol reactions, a potential source of functionalized hydroperoxides in the atmosphere

McGillen, Max R., Curchod, Basile F.E., Chhantyal-Pun, Rabi, Beames, Joseph, Watson, Nathan, Khan, M. Anwar H., McMahon, Laura, Shallcross, Dudley E. and Orr-Ewing, Andrew J. 2017. Criegee intermediate-alcohol reactions, a potential source of functionalized hydroperoxides in the atmosphere. ACS Earth and Space Chemistry 1 (10) , pp. 664-672. 10.1021/acsearthspacechem.7b00108

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Abstract

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.

Item Type: Article
Date Type: Publication
Status: Published
Schools: Chemistry
Publisher: American Chemical Society
ISSN: 2472-3452
Funders: NERC
Date of First Compliant Deposit: 10 January 2018
Date of Acceptance: 14 November 2017
Last Modified: 23 Jan 2018 14:29
URI: http://orca.cf.ac.uk/id/eprint/108048

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