Multiphase Ozonolysis of Aqueous α-Terpineol.
Multiphase ozonolysis of aqueous organics presents a potential pathway for the formation of aqueous secondary organic aerosol (aqSOA). We investigated the multiphase ozonolysis of α-terpineol, an oxygenated derivative of limonene, and found that the reaction products and kinetics differ from the gas-phase ozonolysis of α-terpineol. One- and two-dimensional NMR spectroscopies along with GC-MS identified the aqueous ozonolysis reaction products as trans- and cis-lactols [4-(5-hydroxy-2,2-dimethyltetrahydrofuran-3-yl)butan-2-one] and a lactone [4-hydroxy-4-methyl-3-(3-oxobutyl)-valeric acid gamma-lactone], which accounted for 46%, 27%, and 20% of the observed products, respectively. Hydrogen peroxide was also formed in 10% yield consistent with a mechanism involving decomposition of hydroxyl hydroperoxide intermediates followed by hemiacetal ring closure. Multiphase reaction kinetics at gaseous ozone concentrations of 131, 480, and 965 parts-per-billion were analyzed using a resistance model of net ozone uptake and found the second-order rate coefficient for the aqueous reaction of α-terpineol + O3to be 9.9(±3.3) × 106M-1s-1. Multiphase ozonolysis will therefore be competitive with multiphase oxidation by hydroxyl radicals (OH) and ozonolysis of gaseous α-terpineol. We also measured product yields for the heterogeneous ozonolysis of α-terpineol adsorbed on glass, NaCl, and kaolinite, and identified the same three major products but with an increasing lactone yield of 33, 49, and 55% on these substrates, respectively.
Department of Chemistry, Drew University , Madison, New Jersey 07940, United States.
Dani H
DH
Leviss
Department of Chemistry, Drew University , Madison, New Jersey 07940, United States.
Daryl A
DA
Van Ry
Department of Chemistry, Drew University , Madison, New Jersey 07940, United States.
Ryan Z
RZ
Hinrichs
D000336:Aerosols / Q000737:chemistry*; D017665:Hydroxyl Radical / Q000737:chemistry; D010084:Oxidation-Reduction; D010126:Ozone / Q000737:chemistry*; D014867:Water
D000336:Aerosols; D014867:Water; D017665:Hydroxyl Radical; D010126:Ozone