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New Insights into the Radical Chemistry and Product Distribution in the OH-Initiated Oxidation of Benzene

Xu, Lu and Møller, Kristian H. and Crounse, John D. and Kjaergaard, Henrik G. and Wennberg, Paul O. (2020) New Insights into the Radical Chemistry and Product Distribution in the OH-Initiated Oxidation of Benzene. Environmental Science and Technology, 54 (21). pp. 13467-13477. ISSN 0013-936X. doi:10.1021/acs.est.0c04780.

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Emissions of aromatic compounds cause air pollution and detrimental health effects. Here, we explore the reaction kinetics and products of key radicals in benzene photo-oxidation. After initial OH addition and reaction with O₂, the effective production rates of phenol and bicyclic peroxy radical (BCP-peroxy) are experimentally constrained at 295 K to be 420 ± 80 and 370 ± 70 s⁻¹, respectively. These rates lead to approximately 53% yield for phenol and 47% yield for BCP-peroxy under atmospheric conditions. The reaction of BCP-peroxy with NO produces bicyclic hydroxy nitrate with a branching ratio <0.2%, indicating efficient NO_x recycling. Similarly, the reaction of BCP-peroxy with HO₂ largely recycles HO_x, producing the corresponding bicyclic alkoxy radical (BCP-oxy). Because of the presence of C–C double bonds and multiple functional groups, the chemistry of BCP-oxy and other alkoxy radicals in the system is diverse. Experimental results suggest the aldehydic H-shift and ring-closure to produce an epoxide functionality could be competitive with classic decomposition of alkoxy radicals. These reactions are potential sources of highly oxygenated molecules. Finally, despite the large number of compounds observed in our study, we are unable to account for ∼20% of the carbon flow.

Item Type:Article
Related URLs:
URLURL TypeDescription
Xu, Lu0000-0002-0021-9876
Møller, Kristian H.0000-0001-8070-8516
Crounse, John D.0000-0001-5443-729X
Kjaergaard, Henrik G.0000-0002-7275-8297
Wennberg, Paul O.0000-0002-6126-3854
Additional Information:© 2020 American Chemical Society. Received 17 July 2020. Accepted 6 October 2020. Revised 5 October 2020. Published online 21 October 2020. L.X., J.D.C., and P.O.W. thank NASA (NNX14AP46G) and NSF (CHE-1905340) for supporting this work. K.H.M. and H.G.K. acknowledge funding from the University of Copenhagen and the Independent Research Fund Denmark. The authors declare no competing financial interest.
Funding AgencyGrant Number
University of CopenhagenUNSPECIFIED
Independent Research Fund DenmarkUNSPECIFIED
Subject Keywords:Hydrocarbons, Anions, Aromatic compounds, Oxidation, Molecular structure
Issue or Number:21
Record Number:CaltechAUTHORS:20201021-151807739
Persistent URL:
Official Citation:New Insights into the Radical Chemistry and Product Distribution in the OH-Initiated Oxidation of Benzene. Lu Xu, Kristian H. Møller, John D. Crounse, Henrik G. Kjaergaard, and Paul O. Wennberg. Environmental Science & Technology 2020 54 (21), 13467-13477; DOI: 10.1021/acs.est.0c04780
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:106193
Deposited By: George Porter
Deposited On:21 Oct 2020 22:48
Last Modified:16 Nov 2021 18:51

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