Stoichiometry of Ozonation of Environmentally Relevant Olefins in Saturated Hydrocarbon Solvents

• Published in: Environmental science & technology 2008-05, Vol.42 (10), p.3582-3587
• Main Authors: Gomez, Anthony L, Lewis, Tanza L, Wilkinson, Stacy A, Nizkorodov, Sergey A
• Format: Article
• Language: English
• Subjects: Alkenes - chemistry; Applied sciences; Environmental Processes; Environmental science; Exact sciences and technology; Fatty acids; Free radicals; Hydrocarbons; Ions; Monoterpenes; Oxidation; Ozonation; Ozone; Ozone - chemistry; Pollution; Q1; saturated hydrocarbons; Solvents; Solvents - chemistry; Temperature
• ISSN: 0013-936X; 1520-5851
• DOI: 10.1021/es800096d

The double bond-to-ozone reaction stoichiometry was quantified for ozonation of several environmentally relevant unsaturated fatty acids and monoterpenes in saturated hydrocarbon solvents. Olefins with initial concentrations from 30 µM to 3 mM were injected in a solvent (n-hexadecane, nonane, or cyclohexane) while an ozone-oxygen mixture was slowly bubbled through the solution. The number of ozone molecules consumed by the injection was quantified in the outgoing flow, and the expected 1:1 double bond-to-ozone reaction stoichiometry was observed only under subambient temperature conditions (T < 250 K). At room temperature, the effective number of double bonds oxidized by each ozone molecule increased to 2−5, with a higher degree of oxidation occurring at lower initial olefin concentrations. The observed enhancement in the stoichiometry is consistent with a competition between direct ozonation and free radical initiated oxidation of double bonds, with free radicals being produced by slow reactions between dissolved ozone and solvent molecules.