Mechanistic Insights into Criegee Intermediate-Hydroperoxyl Radical Chemistry

Li, Bai1; Kumar, Manoj2; Zhou, Chuan1; Li, Lei1; Francisco, Joseph S.2

2022-08-01

10.1021/jacs.2c05346

Journal of the American Chemical Society   Impact Factor & Quartile

0002-7863

1520-5126

The reaction between a Criegee intermediate and the hydroperoxyl radical (HO2) is believed to play a role in the formation of new particles in the troposphere. Although the reaction has been previously studied in the gas phase, there are several knowledge gaps that still need to be filled. We simulated the reaction of anti-CH3CHOO with HO2 and HO2-H2O radical complexes in the gas phase at 0 K, which exhibited a low-barrier profile for water-containing systems and a barrierless profile for water-free systems. Moreover, the reaction was found to follow a proton-transfer mechanism, which challenges previous assumptions that the gas-phase reaction involves a hydrogen atom transfer. The HO2 radical was found to mediate the Criegee hydration reaction in the gas phase. Metadynamics simulations further confirmed that the expected radical adduct formation between anti-CH3CHOO and the HO2 radical, as well as the HO2- and H2O-mediated reactions in the gas phase, followed a concerted mechanism. By combining constrained ab initio molecular dynamics simulations with thermodynamic integration, we quantitively evaluated the free-energy barriers at high temperatures. The barriers obtained for all three Criegee-HO2 reaction systems were found to be temperature-dependent. We also compared the free-energy barriers of water-free and water-containing systems; the results revealed that water could hinder the reaction between the Criegee and HO2 radical. These results suggest that HO2 radicals may be involved in the formation of tropospheric radical adducts, and water molecules may also play important roles in the reactions of Criegee intermediates.

SCI ; EI

English

NI Journal Papers

First ; Corresponding

National Natural Science Foundation of China[22179058] ; Guangdong Provincial Department of Education Innovation Team Program[2021KCXTD012]

Chemistry

Chemistry, Multidisciplinary

WOS:000836090500001

AMER CHEMICAL SOC

20223412598732

Atoms ; Energy barriers ; Free energy ; Free radical reactions ; Gases ; Molecules ; Phase interfaces ; Reaction intermediates ; Reaction kinetics ; Troposphere

Atmospheric Properties:443.1 ; Thermodynamics:641.1 ; Physical Chemistry:801.4 ; Chemical Reactions:802.2 ; Chemical Products Generally:804 ; Atomic and Molecular Physics:931.3

Web of Science

1.Southern Univ Sci & Technol, Dept Mat Sci & Engn, Shenzhen 518055, Peoples R China
2.Univ Penn, Dept Chem, Philadelphia, PA 19104 USA

Li, Bai,Kumar, Manoj,Zhou, Chuan,et al. Mechanistic Insights into Criegee Intermediate-Hydroperoxyl Radical Chemistry[J]. Journal of the American Chemical Society,2022,144:14740-14747.

Li, Bai,Kumar, Manoj,Zhou, Chuan,Li, Lei,&Francisco, Joseph S..(2022).Mechanistic Insights into Criegee Intermediate-Hydroperoxyl Radical Chemistry.Journal of the American Chemical Society,144,14740-14747.

Li, Bai,et al."Mechanistic Insights into Criegee Intermediate-Hydroperoxyl Radical Chemistry".Journal of the American Chemical Society 144(2022):14740-14747.