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Atmospheric Chemistry of Chloroprene Initiated by OH Radicals: Combined Ab Initio/DFT Calculations and Kinetics Analysis

Year: 2024

Type: article

Abstract: High Resolution Image Download MS PowerPoint Slide Chloroprene (CP; CH 2 ═C(Cl)–CH═CH 2 ) is a significant toxic airborne pollutant, often originating from anthropogenic activities. However, the environmental fate of CP is incompletely understood. High level CCSD(T)/aug-cc-pVTZ//M06-2X/aug-cc-pVTZ calculations combined with kinetic modeling were employed here to glean new insight into the reaction mechanism, energies, and kinetics of the reaction of CP with OH radical ( • OH). We report the energies of four different addition pathways and six different abstraction pathways. The • OH attack on the terminal C 1 atom of the =CH 2 group (which is directly attached to the =CCl moiety), leading to the formation of HOCH 2 – • C(Cl)–CH═CH 2, was found to be a major path. The barrier height for the formation of the corresponding transition state was found to be −1.9 kcal mol –1 below that of the starting CP + • OH reactants. Rate coefficients were calculated for addition and abstraction pathways involving the CP + • OH reaction under pre-equilibrium approximation conditions, employing a combination of canonical variational transition state theory and small curvature tunneling. The overall rate coefficient for the reaction of CP + • OH at 298 K was found to be 1.4 × 10 –10 cm 3 molecule –1 s –1 . The thermochemistry of the possible channels and atmospheric implications are provided. In addition, the fate of HOCH 2 – • C(Cl)–CH═CH 2 in the presence of 3 O 2 was investigated. We found the reaction of the CP-derived peroxy radical adduct with HO 2 and NO to make contributions to the formation of products such as formaldehyde, HO 2 radical, Cl atom, HOCH 2 C(OOH)(Cl)CH═CH 2, HOCH 2 C(O)Cl, ClC(O)CH═CH 2, HOCH 2 C(O)CH═CH 2, and HC(O) radical.

Source: The Journal of Physical Chemistry A

DOI: 10.1021/acs.jpca.4c05428

Authors: Parandaman Arathala, Rabi A. Musah

Institutions: Louisiana State University, State University of New York, University at Albany, State University of New York

Language: English

Topic: Atmospheric chemistry and aerosols

Subfield: Atmospheric Science

Field: Earth and Planetary Sciences

Domain: Physical Sciences

Open Access status: hybrid

Funder: National Institute of Justice

Award: Research and Development Using High-level Quantum Chemistry Calculations for the Creation of a Rapid Field Test for the Identification and Differentiation of Hemp and Marijuana