The gas-phase reaction kinetics of different structure of unsaturated alcohols and ketones with O₃

Unsaturated alcohols and ketones are a category of oxygenated biogenic volatile organic compounds, which reacted with tropospheric ozone and then made a significant contribution to the formation of secondary organic aerosols (SOA). However, the chemical pathways of their reaction with O₃ are poorly understood. Hence, the reactions of O₃ with three unsaturated alcohols and ketones were conducted in 100 L FEP Teflon smog chamber and the rate constants were obtained by using the absolute rate method. The rate constant of 4-methyl-3-penten-2-one, 2-methyl-4-penten-2-ol, 4-penten-2-ol reacting with O₃ at 298 K and 760 Torr was (7.68 ± 0.80) × 10⁻¹⁸, (4.27 ± 0.44) × 10⁻¹⁸ and (5.40 ± 0.57) × 10⁻¹⁸ cm³molecule⁻¹s⁻¹, respectively. Combining with theoretical calculation, the factors leading to the different rate constants of a series of similar structure compounds were analyzed, including the steric effect of methyl in specific position and the electron withdrawing effect of hydroxyl group in the gamma position for alcohols and carbonyl group in the beta position for ketones. Moreover, the major products of three unsaturated organics reacted with ozone were detected, and the reaction mechanisms were deduced by further supporting of theoretical calculation. The atmospheric lifetime of the target compounds and the environmental significant were explored.