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Pasik D, Frandsen BN, Meder M, Iyer S, Kurtén T, Myllys N. Gas-Phase Oxidation of Atmospherically Relevant Unsaturated Hydrocarbons by Acyl Peroxy Radicals. J Am Chem Soc 2024; 146:13427-13437. [PMID: 38712858 DOI: 10.1021/jacs.4c02523] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/08/2024]
Abstract
This study assesses the atmospheric impact of reactions between unsaturated hydrocarbons such as isoprene and monoterpenes and peroxy radicals containing various functional groups. We find that reactions between alkenes and acyl peroxy radicals have reaction rates high enough to be feasible in the atmosphere and lead to high molar mass accretion products. Moreover, the reaction between unsaturated hydrocarbons and acyl peroxy radicals leads to an alkyl radical, to which molecular oxygen rapidly adds. This finding is confirmed by both theoretical calculations and experiments. The formed perester peroxy radical may either undergo further H-shift reactions or react bimolecularly. The multifunctional oxygenated compounds formed through acyl peroxy radical + alkene reactions are potentially important contributors to particle formation and growth. Thus, acyl peroxy radical-initiated oxidation chemistry may need to be included in atmospheric models.
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Affiliation(s)
- Dominika Pasik
- Department of Chemistry, University of Helsinki, Helsinki 00014, Finland
- Institute for Atmospheric and Earth System Research, University of Helsinki, Helsinki 00014, Finland
| | - Benjamin N Frandsen
- Department of Chemistry, University of Helsinki, Helsinki 00014, Finland
- Aerosol Physics Laboratory, Tampere University, Tampere 33014, Finland
| | - Melissa Meder
- Institute for Atmospheric and Earth System Research, University of Helsinki, Helsinki 00014, Finland
| | - Siddharth Iyer
- Aerosol Physics Laboratory, Tampere University, Tampere 33014, Finland
| | - Theo Kurtén
- Department of Chemistry, University of Helsinki, Helsinki 00014, Finland
- Institute for Atmospheric and Earth System Research, University of Helsinki, Helsinki 00014, Finland
| | - Nanna Myllys
- Department of Chemistry, University of Helsinki, Helsinki 00014, Finland
- Institute for Atmospheric and Earth System Research, University of Helsinki, Helsinki 00014, Finland
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Zou Y, Yu F, Liu X, Zu L. CH 3O Substitution Effect Revisited in the Vibrationally Resolved Laser-Induced Fluorescence Spectra of Methoxycyclohexoxy Radicals. J Phys Chem A 2024; 128:1025-1031. [PMID: 38301214 DOI: 10.1021/acs.jpca.3c07154] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2024]
Abstract
The oxy-substituted alkoxy radicals have attracted wide attention due to the increasing application of oxygenated volatile organic compounds as fuel additives and solvents. Direct detection of these intermediate radicals is desired for measuring the reaction rate and investigating the oxidation mechanism of organic compounds in the atmosphere. A charge-transfer excited state induced by CH3O substitution was identified in our previous study of 3-methoxy-1-propoxy radical [Xue, J. Phys. Chem. Chem. Phys. 2021, 23, 2586]. As the C-C bonds of chain alkoxy radicals can freely rotate, further studies are needed to understand the mechanism of this long-range charge-transfer effect. In this work, vibrational-resolved laser-induced fluorescence (LIF) spectra of 3- and 4-methoxycyclohexoxy radicals were obtained under jet-cooled conditions. A large red-shift of ∼454 cm-1 of the origin band was observed when the CH3O substituent moved from the δ site to the γ site of the cyclohexoxy radical. The LIF spectra are assigned to 3-cis (e, e) and 4-trans (e, e) conformers, respectively, with the assistance of structural optimization and electron excitation studies conducted at the CAM-B3LYP/6-311++G(d,p) level of theory. Natural transition orbital analysis reveals that the intramolecular charge transfer from the C-O-C p orbital to the radical O p orbital in 3-methoxycyclohexoxy has a strong effect on the radical CO σ → O p excitation and hence results in a spectral change. On the other hand, the spectral effect of CH3O substitution almost vanishes at δ carbon. The results propose a through-bond interaction between CH3O and radical CO groups.
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Affiliation(s)
- Yizhen Zou
- College of Chemistry, Beijing Normal University, Beijing 100875, P. R. China
| | - Fengming Yu
- College of Chemistry, Beijing Normal University, Beijing 100875, P. R. China
| | - Xiaoyu Liu
- College of Chemistry, Beijing Normal University, Beijing 100875, P. R. China
| | - Lily Zu
- College of Chemistry, Beijing Normal University, Beijing 100875, P. R. China
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Yu H, Møller KH, Buenconsejo RS, Crounse JD, Kjaergaard HG, Wennberg PO. Atmospheric Photo-Oxidation of 2-Ethoxyethanol: Autoxidation Chemistry of Glycol Ethers. J Phys Chem A 2023; 127:9564-9579. [PMID: 37934888 DOI: 10.1021/acs.jpca.3c04456] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2023]
Abstract
We investigate the gas-phase photo-oxidation of 2-ethoxyethanol (2-EE) initiated by the OH radical with a focus on its autoxidation pathways. Gas-phase autoxidation─intramolecular H-shifts followed by O2 addition─has recently been recognized as a major atmospheric chemical pathway that leads to the formation of highly oxygenated organic molecules (HOMs), which are important precursors for secondary organic aerosols (SOAs). Here, we examine the gas-phase oxidation pathways of 2-EE, a model compound for glycol ethers, an important class of volatile organic compounds (VOCs) used in volatile chemical products (VCPs). Both experimental and computational techniques are applied to analyze the photochemistry of the compound. We identify oxidation products from both bimolecular and autoxidation reactions from chamber experiments at varied HO2 levels and provide estimations of rate coefficients and product branching ratios for key reaction pathways. The H-shift processes of 2-EE peroxy radicals (RO2) are found to be sufficiently fast to compete with bimolecular reactions under modest NO/HO2 conditions. More than 30% of the produced RO2 are expected to undergo at least one H-shift for conditions typical of modern summer urban atmosphere, where RO2 bimolecular lifetime is becoming >10 s, which implies the potential for glycol ether oxidation to produce considerable amounts of HOMs at reduced NOx levels and elevated temperature. Understanding the gas-phase autoxidation of glycol ethers can help fill the knowledge gap in the formation of SOA derived from oxygenated VOCs emitted from VCP sources.
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Affiliation(s)
- Hongmin Yu
- Division of Geological and Planetary Sciences, California Institute of Technology, 1200 E California Blvd., Pasadena, California 91125, United States
| | - Kristian H Møller
- Department of Chemistry, University of Copenhagen, Universitetsparken 5, Copenhagen Ø DK-2100, Denmark
| | - Reina S Buenconsejo
- Division of Chemistry and Chemical Engineering, California Institute of Technology, 1200 E California Blvd., Pasadena, California 91125, United States
| | - John D Crounse
- Division of Geological and Planetary Sciences, California Institute of Technology, 1200 E California Blvd., Pasadena, California 91125, United States
| | - Henrik G Kjaergaard
- Department of Chemistry, University of Copenhagen, Universitetsparken 5, Copenhagen Ø DK-2100, Denmark
| | - Paul O Wennberg
- Division of Geological and Planetary Sciences, California Institute of Technology, 1200 E California Blvd., Pasadena, California 91125, United States
- Division of Engineering and Applied Science, California Institute of Technology, 1200 E California Blvd., Pasadena, California 91125, United States
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Kjærgaard ER, Møller KH, Kjaergaard HG. Atmospheric Oxidation of Hydroperoxy Amides. J Phys Chem A 2023; 127:9311-9321. [PMID: 37877667 DOI: 10.1021/acs.jpca.3c04509] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2023]
Abstract
Recently, hydroperoxy amides were identified as major products of OH-initiated autoxidation of tertiary amines in the atmosphere. The formation mechanism is analogous to that found for ethers and sulfides but substantially faster. However, the atmospheric fate of the hydroperoxy amides remains unknown. Using high-level theoretical methods, we study the most likely OH-initiated oxidation pathways of the hydroperoxy and dihydroperoxy amides derived from trimethylamine autoxidation. Overall, we find that the OH-initiated oxidation of the hydroperoxy amides predominantly leads to the formation of imides under NO-dominated conditions and more highly oxidized hydroperoxy amides under HO2-dominated conditions. Unimolecular reactions are found to be surprisingly slow, likely due to the restricting, planar structure of the amide moiety.
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Affiliation(s)
- Eva R Kjærgaard
- Department of Chemistry, University of Copenhagen, Universitetsparken 5, DK-2100 Copenhagen Ø, Denmark
| | - Kristian H Møller
- Department of Chemistry, University of Copenhagen, Universitetsparken 5, DK-2100 Copenhagen Ø, Denmark
| | - Henrik G Kjaergaard
- Department of Chemistry, University of Copenhagen, Universitetsparken 5, DK-2100 Copenhagen Ø, Denmark
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Burkholder JB, Orlando JJ. Advances in Atmospheric Chemical and Physical Processes. J Phys Chem A 2023; 127:561-564. [PMID: 36700331 DOI: 10.1021/acs.jpca.2c08865] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Affiliation(s)
- James B Burkholder
- NOAA Chemical Sciences Laboratory, Boulder 80305, Colorado, United States
| | - John J Orlando
- NCAR Atmospheric Chemistry Observations and Modeling Laboratory, Boulder 80305, Colorado, United States
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