Studies of the Gas Phase Reactions of Linalool, 6-Methyl- 5-hepten-2-ol and 3-Methyl-1-penten-3-ol with O3 and OH Radicals

Abstract : The reactions of three unsaturated alcohols (linalool, 6-methyl-5-hepten-2-ol, and 3-methyl-1-penten-3-ol) with ozone and OH radicals have been studied using simulation chambers at T ∼ 296 K and P ∼ 760 Torr. The rate coefficient values (in cm3 molecule−1 s−1) determined for the three compounds are linalool, kO3 = (4.1 ± 1.0) × 10−16 and kOH = (1.7 ± 0.3) × 10−10; 6-methyl-5-hepten-2-ol, kO3 = (3.8 ± 1.2) × 10−16 and kOH = (1.0 ± 0.3) × 10−10; and 3-methyl-1-penten-3-ol, kO3 = (5.2 ± 0.6) × 10−18 and kOH = (6.2 ± 1.8) × 10−11. From the kinetic data it is estimated that, for the reaction of O3 with linalool, attack at the R−CHC(CH3)2 group represents around (93 ± 52)% (k6‑methyl‑5‑hepten‑2‑ol/klinalool) of the overall reaction, with reaction at the R−CHCH2 group accounting for about (1.3 ± 0.5)% (k3‑methyl‑1‑penten‑3‑ol/klinalool). In a similar manner it has been calculated that for the reaction of OH radicals with linalool, attack of the OH radical at the R−CHC(CH3)2 group represents around (59 ± 18)% (k6‑methyl‑5‑hepten‑2‑ol/klinalool) of the total reaction, while addition of OH to the R−CHCH2 group is estimated to be around (36 ± 6)% (k3‑methyl‑1‑penten‑3‑ol/klinalool). Analysis of the products from the reaction of O3 with linalool confirmed that addition to the R−CHC(CH3)2 group is the predominant reaction pathway. The presence of formaldehyde and hydroxyacetone in the reaction products together with compelling evidence for the generation of OH radicals in the system indicates that the hydroperoxide channel is important in the loss of the biradical [(CH3)2COO]* formed in the reaction of O3 with linalool. Studies on the reactions of O3 with the unsaturated alcohols showed that the yields of secondary organic aerosols (SOAs) are higher in the absence of OH scavengers compared to the yields in their presence. However, even under low-NOX concentrations, the reactions of OH radicals with 3-methyl-1-penten-3-ol and 6-methyl-5-hepten-2-ol will make only a minor contribution to SOA formation under atmospheric conditions. Relatively high yields of SOAs were observed in the reactions of OH with linalool, although the initial concentrations of reactants were quite high. The importance of linalool in the formation of SOAs in the atmosphere requires further investigation. The impact following releases of these unsaturated alcohols into the atmosphere are discussed.
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François Bernard, Véronique Daële, Abdelwahid Mellouki. Studies of the Gas Phase Reactions of Linalool, 6-Methyl- 5-hepten-2-ol and 3-Methyl-1-penten-3-ol with O3 and OH Radicals. Journal of Physical Chemistry A, American Chemical Society, 2012, 116, pp.6113-6126. ⟨10.1021/jp211355d⟩. ⟨insu-00874720⟩

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