Multiphase Ozonolysis of Aqueous α-Terpineol

Abstract

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 + O to be 9.9(±3.3) × 10 M s. 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.

The Adsorption of Ozone on the Solid Catalyst Surface and the Catalytic Reaction Mechanism for Organic Components

“…The effect of hydrogen peroxide formed by the decomposition of secondary ozonides in the ozonation of α‐turpentine aqueous solution was confirmed by Leviss and the co‐workers, as shown in Figure 22 [42] …”

“…The mechanism for ozonolysis of aqueous α-terpineol. [42] Reprinted (adapted) with permission from Ref. [42] Copyright 2016, American Chemical Society.…”

“…In the second step, the primary ozonide decomposes to carbonyl compounds and Zwitterionic peroxides (so-called Criegee zwitterion), eq. (42). The last step is the generation of secondary ozonide by carbonyl compound and Zwitterionic peroxide, eq.…”

“…The effect of hydrogen peroxide formed by the decomposition of secondary ozonides in the ozonation of αturpentine aqueous solution was confirmed by Leviss and the co-workers, as shown in Figure 22. [42] In anhydrous ethanol, a reaction mechanism was proposed by catalytic ozonation of cinnamaldehyde to benzaldehyde by CaO, [12p,43] as shown in Figure 23. In the presence of CaO, the selectivity of benzaldehyde reached 59.51 %.…”

“… The mechanism for ozonolysis of aqueous α‐terpineol [42] . Reprinted (adapted) with permission from Ref.…”