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Synthesis and Characterization of Estolide Esters Containing Epoxy and Cyclic Carbonate Groups
- Doll, Kenneth M., Cermak, Steven C., Kenar, James A., Isbell, Terry A.
- The journal of the American Oil Chemists' Society 2016 v.93 no.8 pp. 1149-1155
- Fourier transform infrared spectroscopy, alkenes, carbon dioxide, catalysts, epoxides, esters, ethylene oxide, fatty acids, formic acid, hydrogen peroxide, nuclear magnetic resonance spectroscopy, stable isotopes, tetrabutylammonium compounds, viscosity
- The unsaturated sites in oleic 2-ethylhexyl estolide esters (containing 35 % monoenic fatty acids) were converted into epoxide and five-membered cyclic carbonate groups and the products characterized by Fourier transform infrared spectra (FTIR), ¹H, and ¹³C nuclear magnetic resonance (NMR) spectroscopies. Epoxidation of the alkene bonds was accomplished using performic acid generated in situ from formic acid and hydrogen peroxide. Greater than 90 % alkenes were converted into their corresponding epoxide groups as determined by oxirane values and the epoxide ring structure was confirmed by ¹H and ¹³C NMR. The estolide ester epoxide material was subsequently reacted with supercritical carbon dioxide in the presence of tetrabutylammonium bromide catalyst to produce the corresponding estolide ester containing the cyclic carbonate group. The signals at 1,807 cm⁻¹ and δ 82 ppm in the FTIR and ¹³C-NMR spectra, respectively, confirmed the desired cyclic carbonate was produced. The carbonated estolide ester exhibited a dynamic viscosity, at 25 °C, of 172 mPa·s as compared to 155 mPa·s for the estolide ester starting material. The estolide ester structure of these new derivatives was shown to be consistent throughout their synthesis.