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

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.

Copolymerization of Phthalic Anhydride with Epoxides Catalyzed by Amine-bis(phenolate) Chromium(III) Complexes

The effect of ligand structure on the catalytic activity of amine-bis(phenolate) chromium(III) complexes in the ring-opening copolymerization of phthalic anhydride and a series epoxides was studied. Eight complexes differing in the donor-pendant group (R1) and substituents (R2) in phenolate units were examined as catalysts of the model reaction between phthalic anhydride and cyclohexane oxide in toluene. They were used individually or as a part of the binary catalytic systems with nucleophilic co-catalysts. The co-catalyst was selected from the following organic bases: PPh3, DMAP, 1-butylimidazole, or DBU. The binary catalytic systems turned out to be more active than the complexes used individually, and DMAP proved to be the best choice as a co-catalyst. When the molar ratio of [PA]:[epoxide]:[Cr]:[DMAP] = 250:250:1:1 was applied, the most active complex (R1-X = CH2NMe2, R2 = F) allowed to copolymerize phthalic anhydride with differently substituted epoxides (cyclohexene oxide, 4-vinylcyclohexene oxide, styrene oxide, phenyl glycidyl ether, propylene oxide, butylene oxide, and epichlorohydrin) within 240 min at 110 °C. The resulting polyesters were characterized by Mn up to 20.6 kg mol−1 and narrow dispersity, and they did not contain polyether units.