Kinetic Study of the Atmospheric Oxidation of a Series of Epoxy Compounds by OH Radicals

Abstract

Abstract. The kinetics of the gas-phase reactions of hydroxyl radicals with cyclohexene oxide (CHO), 1,2-epoxyhexane (EHX), 1,2-epoxybutane (12EB), trans-2,3-epoxybutane (tEB) and cis-2,3-epoxybutane (cEB) have been investigated using the relative rate technique. The experiments have been performed at (298 ± 3) K and (760 ± 10) Torr total pressure of synthetic air using different reference compounds in a 1080 l Quartz Reactor (QUAREC) and a 480 l Duran glass chamber. The following room temperature rate coefficients (cm3 molecule−1 s−1) were obtained: k1 (OH+CHO) = (5.93 ± 1.78) × 10−12, k2 (OH+EHX) = (5.77 ± 1.29) × 10−12, k3 (OH+12EB) = (1.98 ± 0.39) × 10−12, k4 (OH+cEB) = (1.50 ± 0.26) × 10−12, k5 (OH+tEB) = (1.81 ± 0.42) × 10−12. With the exception of previous studies for 1,2-epoxybutane and cyclohexene oxide, this is to the best of our knowledge the first kinetic study of the reaction of these compounds with OH radicals. Atmospheric lifetimes, reactivity trends and atmospheric implications are discussed considering the epoxy compound rate coefficients obtained in the present study. In addition to a direct comparison with the literature data where possible, the results from the present study are compared with values estimated from the Structure Activity Relationship method.