Ozonolysis of a series of C7–C9 unsaturated biogenic aldehydes: reactivity study at atmospheric pressure

Abstract

Rate coefficients for the reactions of O₃ with trans-2-heptenal, trans-2-octenal and trans-2-nonenal have been determined at 298 K and (990 ± 10) mbar in an environmental chamber with in situ FTIR spectroscopy. The following rate coefficients in units of k_O3 × 10¹⁸ (cm³ molecule⁻¹ s⁻¹) were obtained: (2.47 ± 0.73) for trans-2-heptenal, (2.37 ± 0.68) for trans-2-octenal and (2.05 ± 0.20) for trans-2-nonenal. It is shown that rate coefficients for the addition of O₃ molecules and OH radicals to the double bond of alkenes and unsaturated and oxygenated volatile organic compounds (OVOCs) at 298 K are related to a good approximation by the expression: log k_OH = 0.16 log k_O3 − 7.55. Furthermore, a correlation between the reactivity of unsaturated VOCs toward O₃ molecules and the energies of the Highest Occupied Molecular Orbit (HOMO) of the unsaturated VOCs is presented and potential atmospheric implications of the results are discussed.