Projects per year
Abstract
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 -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. -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.
Original language | English |
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Pages (from-to) | 1160-1171 |
Number of pages | 12 |
Journal | Physical Chemistry Chemical Physics |
Volume | 21 |
Issue number | 3 |
Early online date | 21 Dec 2018 |
DOIs | |
Publication status | Published - 21 Jan 2019 |
Bibliographical note
© the Owner Societies 2019. This is an author-produced version of the published paper. Uploaded with permission of the publisher/copyright holder. Further copying may not be permitted; contact the publisher for detailsKeywords
- ATMOSPHERIC CHEMISTRY
- PHOTOCHEMISTRY
- Aromatic photochemistry
- Air quality
Profiles
Projects
- 2 Finished
-
EUROCHAMP-2020: Integration of European Simulation Chambers for Investigating Atmospheric Processes – Towards 2020 and beyond
1/12/16 → 31/08/21
Project: Research project (funded) › Research
-
Mechanisms for Atmospheric chemistry: GeneratioN, Interpretation and FidelitY (MAGNIFY)
NATURAL ENVIRONMENT RESEARCH COUNCIL
1/08/15 → 31/01/19
Project: Research project (funded) › Research