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Photochemistry of 2-butenedial and 4-oxo-2-pentenal under atmospheric boundary layer conditions

Lookup NU author(s): Dr Alistair Henderson, Emeritus Professor Bernard Golding



This is the authors' accepted manuscript of an article that has been published in its final definitive form by Royal Society of Chemistry, 2019.

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© 2018 the Owner Societies. Unsaturated 1,4-dicarbonyl compounds, such as 2-butenedial and 4-oxo-2-pentenal are produced in the atmospheric boundary layer from the oxidation of aromatic compounds and furans. These species are expected to undergo rapid photochemical processing, affecting atmospheric composition. In this study, the photochemistry of (E)-2-butenedial and both E and Z isomers of 4-oxo-2-pentenal was investigated under natural sunlight conditions at the large outdoor atmospheric simulation chamber EUPHORE. Photochemical loss rates, relative to j(NO2), are determined to be j((E)-2-butenedial)/j(NO2) = 0.14 (±0.02), j((E)-4-oxo-2-pentenal)/j(NO2) = 0.18 (±0.01), and j((Z)-4-oxo-2-pentenal)/j(NO2) = 0.20 (±0.03). The major products detected for both species are a furanone (30-42%) and, for (E)-2-butenedial, maleic anhydride (2,5-furandione) (12-14%). The mechanism appears to proceed predominantly via photoisomerization to a ketene-enol species following γ-H abstraction. The lifetimes of the ketene-enol species in the dark from 2-butenedial and 4-oxo-2-pentenal are determined to be 465 s and 235 s, respectively. The ketene-enol can undergo ring closure to yield the corresponding furanone, or further unimolecular rearrangement which can subsequently form maleic anhydride. A minor channel (10-15%) also appears to form CO directly. This is presumed to be via a molecular elimination route of an initial biradical intermediate formed in photolysis, with an unsaturated carbonyl (detected here but not quantified) as co-product. α-Dicarbonyl and radical yields are very low, which has implications for ozone production from the photo-oxidation of unsaturated 1,4-dicarbonyls in the boundary layer. Photochemical removal is determined to be the major loss process for these species in the boundary layer with lifetimes of the order of 10-15 minutes, compared to >3 hours for reaction with OH.

Publication metadata

Author(s): Newland MJ, Rea GJ, Thuner LP, Henderson AP, Golding BT, Rickard AR, Barnes I, Wenger J

Publication type: Article

Publication status: Published

Journal: Physical Chemistry Chemical Physics

Year: 2019

Volume: 21

Issue: 3

Pages: 1160-1171

Print publication date: 21/01/2019

Online publication date: 21/12/2018

Acceptance date: 21/12/2018

Date deposited: 04/03/2019

ISSN (print): 1463-9076

ISSN (electronic): 1463-9084

Publisher: Royal Society of Chemistry


DOI: 10.1039/c8cp06437g

PubMed id: 30620029


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