Gas-Phase Ozone Reaction Kinetics of a Series of -3-Hexenyl Esters under Simulated Atmospheric Conditions.

This relative kinetic study presents the experimental results obtained from the investigation of the gas-phase ozonolysis of seven biogenic unsaturated hexenyl esters under atmospheric relevant conditions at a temperature of (298 ± 2) K and a total air pressure of (1000 ± 10) mbar. Various -3-hexenyl esters were selected for the present study since these are ubiquitous biogenic atmospheric constituents emitted by green leaf plants. The series consists of -3-hexenyl formate (3HF), -3-hexenyl acetate (3HAc), -3-hexenyl isobutyrate (3HiB), -3-hexenyl 3-methylbutanoate (3H3MeB), -3-hexenyl hexanoate (3HH), -3-hexenyl -3-hexenoate (3HZ3H), and -3-hexenyl benzoate (3HBz). The obtained experimental gas-phase reaction rate coefficients are as follows (in 10 cm molecule s): (4.5 ± 0.5) for 3HF, (5.5 ± 0.6) for 3HAc, (7.9 ± 0.9) for 3HiB, (11.9 ± 1.3) for 3H3MeB, (15.3 ± 1.7) for 3HH, (22.5 ± 2.5) for 3HZ3H, and (29.1 ± 3.2) for 3HBz, respectively. This study provides the first determination of the gas-phase rate coefficients of ozone with -3-hexenyl isobutyrate, -3-hexenyl 3-methylbutanoate, -3-hexenyl hexanoate, -3-hexenyl -3-hexenoate, and -3-hexenyl benzoate. A comparison of the results with available literature data and structure-activity relationship estimates was performed with emphasis placed on the structural features. The reactivity trend is discussed within this series, and estimates for the photochemical ozone creation potential (POCP) index are provided. Also, the atmospheric average lifetime of the investigated -3-hexenyl esters, with respect to O reaction, and for comparison purposes also to the OH, NO, and Cl driven processes, were evaluated and provided within this study.