Atmospheric oxidation of α, β-unsaturated ketones: kinetics and mechanism of the OH radical reaction

Illmann, Niklas; Gibilisco, Rodrigo Gastón; Bejan, Iustinian Gabriel; Patroescu-Klotz, Iulia; Wiesen, Peter

The OH-radical-initiated oxidation of 3-methyl-3-penten-2-one and 4-methyl-3-penten-2-one was investigated in two atmospheric simulation chambers at inline-formula298±3 K and inline-formula990±15 mbar using long-path FTIR spectroscopy. The rate coefficients of the reactions of 3-methyl-3-penten-2-one and 4-methyl-3-penten-2-one with OH radicals were determined to be inline-formula M7inlinescrollmathml ( normal 6.5 ± normal 1.2 ) × normal 10 - normal 11 89pt15ptsvg-formulamathimgb48c755316b3dbd62722b42b8ad6cf5f acp-21-13667-2021-ie00001.svg89pt15ptacp-21-13667-2021-ie00001.png and inline-formula M8inlinescrollmathml ( normal 8.1 ± normal 1.3 ) × normal 10 - normal 11 89pt15ptsvg-formulamathimg10dc9d57e418424663f074d80792f80c acp-21-13667-2021-ie00002.svg89pt15ptacp-21-13667-2021-ie00002.png inline-formula M9inlinescrollmathml unit normal cm normal 3 nobreak0.125em normal molecule - normal 1 0.125emnobreak normal s - normal 1 94pt13ptsvg-formulamathimg36950893a7eaaa3ce6924f4832c6b47e acp-21-13667-2021-ie00003.svg94pt13ptacp-21-13667-2021-ie00003.png , respectively. To enlarge the kinetics data pool the rate coefficients of the target species with Cl atoms were determined to be inline-formula M10inlinescrollmathml ( normal 2.8 ± normal 0.4 ) × normal 10 - normal 10 89pt15ptsvg-formulamathimg884f6fe3dfa2876bea25504fe6ebac68 acp-21-13667-2021-ie00004.svg89pt15ptacp-21-13667-2021-ie00004.png and inline-formula M11inlinescrollmathml ( normal 3.1 ± normal 0.4 ) × normal 10 - normal 10 89pt15ptsvg-formulamathimg0d5f72c03fae92baf20ad49e73e78945 acp-21-13667-2021-ie00005.svg89pt15ptacp-21-13667-2021-ie00005.png inline-formula M12inlinescrollmathml unit normal cm normal 3 nobreak0.125em normal molecule - normal 1 nobreak0.125em normal s - normal 1 94pt13ptsvg-formulamathimgf4ad566f46a49d2dd86ee547645d13f8 acp-21-13667-2021-ie00006.svg94pt13ptacp-21-13667-2021-ie00006.png , respectively. The mechanistic investigation of the OH-initiated oxidation focuses on the inline-formulaRO2+NO reaction. The quantified products were acetoin, acetaldehyde, biacetyl, inline-formulaCO2 and peroxyacetyl nitrate (PAN) for the reaction of 3-methyl-3-penten-2-one with OH radicals and acetone, methyl glyoxal, 2-hydroxy-2-methylpropanal, inline-formulaCO2 and peroxyacetyl nitrate (PAN) for the reaction of 4-methyl-3-penten-2-one with OH, respectively. Based on the calculated product yields an upper limit of 0.15 was determined for the yield of inline-formulaRONO2 derived from the OH reaction of 4-methyl-3-penten-2-one. By contrast, no inline-formulaRONO2 formation was observed for the OH reaction of 3-methyl-3-penten-2-one. Additionally, a simple model is presented to correct product yields for secondary processes.

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Illmann, Niklas / Gibilisco, Rodrigo Gastón / Bejan, Iustinian Gabriel / et al: Atmospheric oxidation of α,β-unsaturated ketones: kinetics and mechanism of the OH radical reaction. 2021. Copernicus Publications.

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