Thermalized Epoxide Formation in the Atmosphere

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http://hdl.handle.net/10138/322132

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Moller , K H , Kurten , T , Bates , K H , Thornton , J A & Kjaergaard , H G 2019 , ' Thermalized Epoxide Formation in the Atmosphere ' , Journal of Physical Chemistry A , vol. 123 , no. 49 , pp. 10620-10630 . https://doi.org/10.1021/acs.jpca.9b09364

Title: Thermalized Epoxide Formation in the Atmosphere
Author: Moller, Kristian H.; Kurten, Theo; Bates, Kelvin H.; Thornton, Joel A.; Kjaergaard, Henrik G.
Contributor: University of Helsinki, Department of Chemistry
Date: 2019-12-12
Language: eng
Number of pages: 11
Belongs to series: Journal of Physical Chemistry A
ISSN: 1089-5639
URI: http://hdl.handle.net/10138/322132
Abstract: Epoxide formation was established a decade ago as a possible reaction pathway for beta-hydroperoxy alkyl radicals in the atmosphere. This epoxide-forming pathway required excess energy to compete with O-2 addition, as the thermal reaction rate coefficient is many orders of magnitude too slow. However, recently, a thermal epoxide forming reaction was discovered in the ISOPOOH + OH oxidation pathway. Here, we computationally investigate the effect of substituents on the epoxide formation rate coefficient of a series of substituted beta-hydroperoxy alkyl radicals. We find that the thermal reaction is likely to be competitive with O-2 addition when the alkyl radical carbon has a OH group, which is able to form a hydrogen bond to a substituent on the other carbon atom in the epoxide ring being formed. Reactants fulfilling these requirements can be formed in the OH-initiated oxidation of many biogenic hydrocarbons. Further, we find that beta-OOR alkyl radicals react similarly to beta-OOH alkyl radicals, making epoxide formation a possible decomposition pathway in the oxidation of ROOR peroxides. GEOS-Chem modeling shows that the total annual production of isoprene dihydroxy hydroperoxy epoxide is 23 Tg, making it by far the most abundant C-5-tetrafunctional species from isoprene oxidation.
Subject: SECONDARY ORGANIC AEROSOL
MOLECULAR-ORBITAL METHODS
CYCLIC ETHER FORMATION
BASIS-SETS
ISOPRENE EPOXYDIOLS
TROPOSPHERIC CHEMISTRY
ARRHENIUS PARAMETERS
REACTIVE UPTAKE
MODEL
EMISSIONS
116 Chemical sciences
114 Physical sciences
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