Preprints
https://doi.org/10.5194/acp-2021-890
https://doi.org/10.5194/acp-2021-890

  08 Nov 2021

08 Nov 2021

Review status: this preprint is currently under review for the journal ACP.

OH-Initiated Atmospheric Degradation of Hydroxyalkyl Hydroperoxides: Mechanism, Kinetics, and Structure-Activity Relationship

Long Chen1,2, Yu Huang1,2, Yonggang Xue1,2, Zhihui Jia3, and Wenliang Wang4 Long Chen et al.
  • 1State Key Lab of Loess and Quaternary Geology (SKLLQG), Institute of Earth Environment, Chinese Academy of Sciences (CAS), Xi'an, 710061, China
  • 2CAS Center for Excellence in Quaternary Science and Global Change, Xi'an, 710061, China
  • 3School of Materials Science and Engineering, Shaanxi Normal University, Xi'an, Shaanxi, 710119, China
  • 4School of Chemistry and Chemical Engineering, Key Laboratory for Macromolecular Science of Shaanxi Province, Shaanxi Normal University, Xi'an, Shaanxi, 710119, China

Abstract. Hydroxyalkyl hydroperoxides (HHPs), formed in the reactions of Criegee intermediates (CIs) with water vapour, play essential roles in the formation of secondary organic aerosol (SOA) under atmospheric conditions. However, the transformation mechanism for OH-initiated oxidation of HHPs is remain incompletely understood. Herein, the quantum chemical and kinetics modeling methods are applied to insight into the detailed mechanisms of OH-initiated oxidation of distinct HHPs formed form the reactions of CH2OO, anti-CH3CHOO and (CH3)2COO) with water vapor. The calculations show that H-abstraction by OH radical from the -OOH group of distinct HHPs is predominate as the main products peroxyl radicals (RO2), and the barrier of dominant pathway is increased as the number of methyl group is increased. In pristine environments, the self-reaction of RO2 radical initially produces tetroxide intermediate via a head-to-head interaction, then it decomposes into propagation and termination products through the asymmetric two-step O-O bond scission, in which the rate-limiting step is the first O-O bond cleavage. The barrier height of distinct RO2 radicals reactions with HO2 radical is independent on the number of methyl substitution. Compared to the rate coefficient of parent system, it is increased by a factor of 3–5 when one or two methyl groups introduce into the C1-position. The autoxidation of RO2 radicals are unlikely to proceed in the atmosphere due to their dramatically high barriers and strongly endergonic. In urban environments, the rate-limiting step is the hydrogen abstraction by O2 in the processes of HOCH2OO radical reaction with NO, while it becomes the O-O bond scission when one or two methyl substitutions occur at the C1-position of HOCH2OO radical. These new findings are expected to deepen our current understanding for the photochemistry oxidation of hydroperoxides under realistic atmospheric conditions.

Long Chen et al.

Status: open (until 20 Dec 2021)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on acp-2021-890', Anonymous Referee #1, 18 Nov 2021 reply
  • RC2: 'Comment on acp-2021-890', Anonymous Referee #2, 23 Nov 2021 reply

Long Chen et al.

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Short summary
The quantum chemical and kinetics modeling methods are applied to insight into the detailed mechanisms of OH-initiated oxidation of distinct hydroxyalkyl hydroperoxides (HHPs) formed form the reactions of CH2OO, anti-CH3CHOO and (CH3)2COO) with water vapor. The calculations show that H-abstraction by OH radical from the -OOH group of distinct HHPs is predominate as the main products RO2 radicals, and the barrier of dominant pathway is increased as the number of methyl group is increased.
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