Kinetics and mechanisms of gas phase reactions of hexenols with ozone

Abstract

An absolute kinetic study is reported for the reactions of O₃ with a series of C6 hexenols, (Z)-2-hexen-1-ol, (Z)-3-hexen-1-ol, (Z)-4-hexen-1-ol, (E)-2-hexen-1-ol, (E)-3-hexen-1-ol, and (E)-4-hexen-1-ol. At 298 K and atmospheric pressure, the rate constants (in units of 10⁻¹⁷ cm³ molecule⁻¹ s⁻¹) were measured to be 7.44 ± 1.03, 5.47 ± 0.71, 7.09 ± 0.91, 16.6 ± 2.2, 6.19 ± 0.72 and 10.5 ± 1.4, respectively. To gain a deeper insight into the reactivity and mechanism, theoretical calculations were also performed for the title reactions with the methods of density functional theory (DFT) and transition-state theory (TST). The geometries, energies, and harmonic vibrational frequencies of each stationary point were obtained at the BH&HLYP/6-31+G(d,p) level of theory. The calculated rate constants are in good agreement with the experimental data, and the reactivity of hexenols with O₃ shows a strong dependence on their chemical structure based on the theoretical results. Finally, lifetimes of the C6 hexenols, with respect to their reactions with some important atmospheric oxidants such as O₃, OH and NO₃ radicals, have also been discussed in the article.