Abstract
The present relative kinetic study reports on the experimentally determined gas-phase reaction rate coefficients of OH radicals with a series of seven cis-3-hexenyl esters. The experiments were carried out in the environmental simulation chamber made of quartz from the "Alexandru Ioan Cuza" University of Iasi (ESC-Q-UAIC), Romania, at a temperature of (298 ± 2) K and a total air pressure of (1000 ± 10) mbar. In situ long-path Fourier transform infrared (FTIR) spectroscopy was used to monitor cis-3-hexenyl formate (Z3HF, (Z)-CH(3)CH(2)CH═CH(CH(2))(2)OC(O)H), cis-3-hexenyl acetate (Z3HAc, (Z)-CH(3)CH(2)CH═CH(CH(2))(2)OC(O)CH(3)), cis-3-hexenyl isobutyrate (Z3HiB, (Z)-CH(3)CH(2)CH═CH(CH(2))(2)OC(O)CH(CH(3))(2)), cis-3-hexenyl 3-methylbutanoate (Z3H3MeB, (Z)-CH(3)CH(2)CH═CH(CH(2))(2)OC(O)CH(2)CH(CH(3))(2)), cis-3-hexenyl hexanoate (Z3HH, (Z)-CH(3)CH(2)CH═CH(CH(2))(2)OC(O)(CH(2))(4)CH(3)), cis-3-hexenyl cis-3-hexenoate (Z3HZ3H, (Z,Z)-CH(3)CH(2)CH═CH(CH(2))(2)OC(O)CH(2)CH═CHCH(2)CH(3)), cis-3-hexenyl benzoate (Z3HBz, (Z)-CH(3)CH(2)CH═CH(CH(2))(2)OC(O)C(6)H(5)), and the reference compounds. The following reaction rate coefficients (in 10(-11) cm(3) molecule(-1) s(-1)) were obtained for the OH radical-initiated gas-phase oxidation of cis-3-hexenyl esters: (4.13 ± 0.45) for Z3HF, (4.19 ± 0.38) for Z3HAc, (4.84 ± 0.39) for Z3HiB, (5.39 ± 0.61) for Z3H3MeB, (7.00 ± 0.56) for Z3HH, (10.58 ± 1.40) for Z3HZ3H, and (3.41 ± 0.28) for Z3HBz. The results are discussed in terms of hexenyl ester reactivity and compared with the available literature data and structure-activity relationship (SAR) estimates. The atmospheric implications based on the average lifetimes of the investigated cis-3-hexenyl esters are discussed in the present study. The gas-phase rate coefficients for OH radical reactions are given herein for the first time for cis-3-hexenyl isobutyrate, cis-3-hexenyl 3-methylbutanoate, cis-3-hexenyl hexanoate cis-3-hexenyl cis-3-hexenoate, and cis-3-hexenyl benzoate. The newly determined gas-phase reaction rate coefficients provide new information for existing kinetic databases and contribute to the further development of SAR methodologies useful for predicting the reactivity of oxygenated volatile organic compounds.