Formation of Highly Oxidized Radicals and Multifunctional Products from the Atmospheric Oxidation of Alkylbenzenes

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Wang , S , Wu , R , Berndt , T , Ehn , M & Wang , L 2017 , ' Formation of Highly Oxidized Radicals and Multifunctional Products from the Atmospheric Oxidation of Alkylbenzenes ' , Environmental Science & Technology , vol. 51 , no. 15 , pp. 8442-8449 . https://doi.org/10.1021/acs.est.7b02374

Title: Formation of Highly Oxidized Radicals and Multifunctional Products from the Atmospheric Oxidation of Alkylbenzenes
Author: Wang, Sainan; Wu, Runrun; Berndt, Torsten; Ehn, Mikael; Wang, Liming
Contributor organization: Department of Physics
Date: 2017-08-01
Language: eng
Number of pages: 8
Belongs to series: Environmental Science & Technology
ISSN: 0013-936X
DOI: https://doi.org/10.1021/acs.est.7b02374
URI: http://hdl.handle.net/10138/318940
Abstract: Aromatic hydrocarbons contribute significantly to tropospheric ozone and secondary organic aerosols (SOA). Despite large efforts in elucidating the formation mechanism of aromatic-derived SOA, current models still substantially underestimate the SOA yields when comparing to field measurements. Here we present a new, up to now undiscovered pathway for the formation of highly oxidized products from the OH-initiated oxidation of alkyl benzenes based on theoretical and experimental investigations. We propose that unimolecular H-migration followed by O-2-addition, a so-called autoxidation step, can take place in bicyclic peroxy radicals (BPRs), which are important intermediates of the OH -initiated oxidation of aromatic compounds. These autoxidation steps lead to the formation of highly oxidized multifunctional compounds (HOMs), which are able to form SOA. Our theoretical calculations suggest that the intramolecular H-migration in BPRs of substituted benzenes could be fast enough to compete with bimolecular reactions with HO2 radicals or NO under atmospheric conditions. The theoretical findings are experimentally supported by flow tube studies using chemical ionization mass spectrometry to detect the highly oxidized peroxy radical intermediates and closed-shell products. This new unimolecular BPR route to form HOMs in the gas phase enhances our understanding of the aromatic oxidation mechanism, and contributes significantly to a better understanding of aromatic-derived SOA in urban areas.
Subject: SECONDARY ORGANIC AEROSOL
INTRAMOLECULAR HYDROGEN SHIFT
AROMATIC-HYDROCARBONS
PEROXY-RADICALS
M-XYLENE
RO2 RADICALS
OH RADICALS
MECHANISM
TOLUENE
OZONOLYSIS
114 Physical sciences
116 Chemical sciences
1172 Environmental sciences
Peer reviewed: Yes
Usage restriction: openAccess
Self-archived version: acceptedVersion


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