Liquid CO2 as a Safe and Benign Solvent for the Ozonolysis of Fatty Acid Methyl Esters

We have shown that liquid CO2 dissolves O3 in higher concentrations compared to conventional solvents and is therefore an effective medium for the ozonolysis of unsaturated compounds. The Beer–Lambert law extinction coefficient for ozone in liquid CO2 is determined to be 3.2 ± 0.3 M–1 cm–1. Further, the Henry’s law coefficient for ozone dissolution in dense phase CO2 is determined to be on the order of 0.25 mol L–1 bar–1 in the temperature range −10 to +4 °C. Rapid ozonolysis of methyl oleate in liquid CO2 has been successfully demonstrated with the 1,2,4-trioxolanes (secondary ozonides) being the major stable product, as confirmed by NMR analysis. The product distribution is consistent with a lack of solvent cage effects due to the low polarity of liquid CO2. In addition to the inertness of liquid CO2 to ozone attack, the dominant presence of dense CO2 in the vapor phase promotes inherent process safety.