An Experimental Study of the Gas-Phase Reactions of NO₃ Radicals with a Series of Unsaturated Aldehydes: <i>trans</i>-2-Hexenal, <i>trans</i>-2-Heptenal, and <i>trans</i>-2-Octenal

Rate constants for the gas-phase reactions of the NO₃ radical with a series of unsaturated aldehydes, <i>trans</i>-2-hexenal, <i>trans</i>-2-heptenal, and <i>trans</i>-2-octenal, have been measured using absolute rate method at 294 ± 3 K and atmospheric pressure. This work was performed to clarify discrepancies found in the literature and thus led to a clearer view of the effect of the increasing carbon chain length on the reactivity of <i>trans</i>-2-alkenals. The rate constants were determined to be (4.7 ± 1.5) × 10^–15, (5.3 ± 1.6) × 10^–15, and (5.6 ± 2.3) × 10^–15 cm³ molecule^–1 s^–1 for <i>trans</i>-2-hexenal, <i>trans</i>-2-heptenal, and <i>trans</i>-2-octenal, respectively. These results clearly indicate that the carbon chain lengthening of the <i>trans</i>-2-alkenals does not significantly affect the rate constant. In addition, the mechanism for the reaction of NO₃ with these unsaturated aldehydes was also investigated. Unsaturated peroxynitrate-type compounds that are exclusively formed through the abstraction channel were observed as the main products