Atmospheric photooxidation and ozonolysis of Δ ³-carene and 3-caronaldehyde: rate constants and product yields

The oxidation of inline-formulaΔ³-carene and one of its main oxidation products, caronaldehyde, by the inline-formulaOH radical and inline-formulaO₃ was investigated in the atmospheric simulation chamber SAPHIR under atmospheric conditions for inline-formulaNO_x mixing ratios below inline-formula2 inline-formulappbv. Within this study, the rate constants of the reaction of inline-formulaΔ³-carene with inline-formulaOH and inline-formulaO₃ and of the reaction of caronaldehyde with inline-formulaOH were determined to be inline-formula $M12inlinescrollmathml(\mathrm{normal\; 8.0}\pm \mathrm{normal\; 0.5})\times {\mathrm{normal\; 10}}^{-\mathrm{normal\; 11}}$ 89pt15ptsvg-formulamathimg6d57794042b8058842d25c1e4f14befa acp-21-12665-2021-ie00001.svg89pt15ptacp-21-12665-2021-ie00001.png  inline-formulacm³ s⁻¹ at inline-formula304 inline-formulaK, inline-formula $M16inlinescrollmathml(\mathrm{normal\; 4.4}\pm \mathrm{normal\; 0.2})\times {\mathrm{normal\; 10}}^{-\mathrm{normal\; 17}}$ 89pt15ptsvg-formulamathimgcb5c5f2d74cd002b6408bf8d3f9b3e59 acp-21-12665-2021-ie00002.svg89pt15ptacp-21-12665-2021-ie00002.png  inline-formulacm³ s⁻¹ at inline-formula300 inline-formulaK and inline-formula $M20inlinescrollmathml(\mathrm{normal\; 4.6}\pm \mathrm{normal\; 1.6})\times {\mathrm{normal\; 10}}^{-\mathrm{normal\; 11}}$ 89pt15ptsvg-formulamathimg2b450bfd508a10cb6d05262cda6108d6 acp-21-12665-2021-ie00003.svg89pt15ptacp-21-12665-2021-ie00003.png  inline-formulacm³ s⁻¹ at inline-formula300 inline-formulaK, in agreement with previously published values. The yields of caronaldehyde from the reaction of inline-formulaOH and ozone with inline-formulaΔ³-carene were determined to be inline-formula0.30±0.05 and inline-formula0.06±0.02, respectively. Both values are in reasonably good agreement with reported literature values. An organic nitrate (inline-formulaRONO₂) yield from the reaction of inline-formulaNO with inline-formulaRO₂ derived from inline-formulaΔ³-carene of inline-formula0.25±0.04 was determined from the analysis of the reactive nitrogen species (inline-formulaNOinline-formula_y) in the SAPHIR chamber. The inline-formulaRONO₂ yield of the reaction of inline-formulaNO with inline-formulaRO₂ derived from the reaction of caronaldehyde with inline-formulaOH was found to be inline-formula0.10±0.02. The organic nitrate yields of inline-formulaΔ³-carene and caronaldehyde oxidation with inline-formulaOH are reported here for the first time in the gas phase. An inline-formulaOH yield of inline-formula0.65±0.10 was determined from the ozonolysis of inline-formulaΔ³-carene. Calculations of production and destruction rates of the sum of hydroxyl and peroxy radicals (inline-formula $M45inlinescrollmathml{chem\mathrm{normal\; RO}}_x=chem\mathrm{normal\; OH}+chem{\mathrm{normal\; HO}}_{\mathrm{normal\; 2}}+chem{\mathrm{normal\; RO}}_{\mathrm{normal\; 2}}$ 117pt13ptsvg-formulamathimg3cfb6ac81805f4c4be8eb47e351f13c0 acp-21-12665-2021-ie00004.svg117pt13ptacp-21-12665-2021-ie00004.png ) demonstrated that there were no unaccounted production or loss processes of radicals in the oxidation of inline-formulaΔ³-carene for conditions of the chamber experiments. In an inline-formulaOH-free experiment with added inline-formulaOH scavenger, the photolysis frequency of caronaldehyde was obtained from its photolytical decay. The experimental photolysis frequency was a factor of 7 higher than the value calculated from the measured solar actinic flux density, an absorption cross section from the literature and an assumed effective quantum yield of unity for photodissociation.