Bimolecular sinks of Criegee intermediates derived from hydrofluoroolefins – a computational analysis

Watson, Nathan A. I. and Beames, Joseph M. ORCID: https://orcid.org/0000-0002-5508-8236 2023. Bimolecular sinks of Criegee intermediates derived from hydrofluoroolefins – a computational analysis. Environmental Science: Atmospheres 3 , pp. 1460-1484. 10.1039/d3ea00102d

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Abstract

A novel range of stabilised Criegee intermediate (sCI) species with halogenated substituent groups have been identified as products to the reaction between with gaseous ozone and hydrofluoroolefins (HFOs), a series of recently-developed and increasingly prevalent haloalkene refrigerants. The bimolecular chemistry of this group of hydrofluoroolefin-derived sCIs (HFO-sCIs) has yet to be explored in any significant detail so this work evaluates the reaction chemistry of common tropospheric gaseous species with the following group of HFO-sCIs: syn- & anti-CF3CHOO & syn- & anti-CF3CFOO. Using high-level theoretical calculations (DF-HF/DF-LCCSD(T)-F12a//B3LYP/aug-cc-pVTZ), this study demonstrates that HFO-sCIs will deplete many pollutants (e.g. HCHO, SO2 & H2S) but also act as a source of other atmospheric contaminants (e.g. SO3 & TFA). The bimolecular reactivity of the HFO-sCIs were compared against CH2OO, the most frequently studied sCI, for which the general reactivity trend has been identified: kTHEO (syn-CF3CHOO) < kTHEO (anti-CF3CHOO) ≈ kTHEO (CH2OO) ≪ kTHEO (anti-CF3CFOO) < kTHEO (syn-CF3CFOO). In general syn & anti-CF3 substituents reduce overall sCI reactivity compared to similar non-halogenated sCI species, whereas both syn & anti-F substituents significantly increase HFO-sCI reactivity. While HFO-sCI reactivity is largely dictated by the identity and location of the sCI substituent groups, there are co-reactants that alter these observed trends in reactivity, for example HCl reacts more rapidly with CH2OO than it does with syn- & anti-CF3CFOO.

Item Type:	Article
Date Type:	Publication
Status:	Published
Schools:	Chemistry
Additional Information:	License information from Publisher: LICENSE 1: URL: http://creativecommons.org/licenses/by/3.0/, Start Date: 2023-08-17
Publisher:	Royal Society of Chemistry
ISSN:	2634-3606
Date of First Compliant Deposit:	23 August 2023
Date of Acceptance:	15 August 2023
Last Modified:	26 Oct 2023 14:19
URI:	https://orca.cardiff.ac.uk/id/eprint/161991

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