Issue 35, 2021

Reactions of organic peroxy radicals, RO2, with substituted and biogenic alkenes at room temperature: unsuspected sinks for some RO2 in the atmosphere?

Abstract

Until now the reactions of organic peroxy radicals (RO2) with alkenes in the gas phase have been essentially studied at high temperature (T ≥ 360 K) and in the context of combustion processes, while considered negligible in the Earth's atmosphere. In this work, the reactions of methyl-, 1-pentyl- and acetylperoxy radicals (CH3O2, C5H11O2, and CH3C(O)O2, respectively) with 2-methyl-2-butene, 2,3-dimethyl-2-butene and for the first time the atmospherically relevant isoprene, α-pinene, and limonene were studied at room temperature (298 ± 5 K). Monitoring directly the radicals with chemical ionization mass spectrometry led to rate coefficients larger than expected from previous combustion studies but following similar trends in terms of alkenes, with (in molecule−1 cm3 s−1) Image ID:d1sc02263f-t1.gif = 10−18 to 10−17 × 2/2 and Image ID:d1sc02263f-t2.gif = 10−14 to 10−13 × 5/5. While these reactions would be negligible for CH3O2 and aliphatic RO2 at room temperature, this might not be the case for acyl-, and perhaps hydroxy-, allyl- and other substituted RO2. Combining our results with the Structure–Activity Relationship (SAR) predicts kII(298 K) ∼10−14 molecule−1 cm3 s−1 for hydroxy- and allyl-RO2 from isoprene oxidation, potentially accounting for up to 14% of their sinks in biogenic-rich regions of the atmosphere and much more in laboratory studies.

Graphical abstract: Reactions of organic peroxy radicals, RO2, with substituted and biogenic alkenes at room temperature: unsuspected sinks for some RO2 in the atmosphere?

Supplementary files

Article information

Article type
Edge Article
Submitted
23 apr 2021
Accepted
25 jul 2021
First published
27 jul 2021
This article is Open Access

All publication charges for this article have been paid for by the Royal Society of Chemistry
Creative Commons BY-NC license

Chem. Sci., 2021,12, 11676-11683

Reactions of organic peroxy radicals, RO2, with substituted and biogenic alkenes at room temperature: unsuspected sinks for some RO2 in the atmosphere?

B. Nozière and F. Fache, Chem. Sci., 2021, 12, 11676 DOI: 10.1039/D1SC02263F

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