Submitted to: Journal of the American Oil Chemists' Society
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: May 20, 2003
Publication Date: September 20, 2003
Citation: Piazza, G.J., Nunez, A., Foglia, T.A. 2003. Hydrolysis of mono- and diepoxyoctadecanoates by alumina. Journal of the American Oil Chemists' Society. 80(9):901-904. Interpretive Summary: Conversion of fats and oils and their derivatives to polyhydroxy materials may be desirable, as these materials are suitable for several industrial applications such as metal working lubricants, waxes, and urethanes. The present procedure for making these polyhydroxy materials uses osmium tetroxide and unsaturated fats or oils. Osmium tetroxide, however, is expensive and highly toxic, so that its use has been limited to small-scale preparations. An alternative route for the synthesis of these polyhydroxy materials is through the hydrolysis of epoxides made from fats and oils. Heretofore, however, this method has required an acid catalyst or an expensive enzymatic catalyst. We investigated epoxide hydrolysis using a commercial preparation of neutral alumina, and we found that alumina readily hydrolyzes fatty methyl ester epoxides to give dihydroxy products. Alumina is superior to an acid catalyst because it is easily removed from the product. Also, for industrial use, alumina is preferred because it is safe, low in cost, and has a long shelf life. This research will aid in the development of a cost-effective procedure for preparing polyhydroxy fatty materials from renewable agricultural materials.
Technical Abstract: The main advantage of heterogeneous catalysis is that the catalyst can be easily separated from the reaction products and reused. There is, therefore, a continuing interest in the preparation of heterogenized catalysts, homogeneous catalysts that have been placed upon an insoluble support. One area of interest is the placement of transition metal complexes onto alumina (aluminum oxide) supports to promote oxidation, particularly epoxide formation. In the subsequent oxidation reactions, it is generally assumed that the alumina acts as an inert support. However, there is reason to be skeptical of this, since prior work has shown that alumina catalyzes nucleophilic addition of alcohols and amines to epoxides. In this study it is shown that the epoxide derivative of oleic acid, methyl 9,10-epoxyoctadecanoate (methyl stearate monoepoxide), is readily hydrolyzed to a diol when exposed to a commercial preparation of neutral alumina. Comparison of proton and carbon 13 NMR spectra of the diol with those of standards showed that the product was the threo isomer. Time course studies showed that the epoxide was converted to diol in 4 h. When methyl 9,10-12,13-diepoxy octadecanoate (methyl stearate diepoxide) was treated with alumina, a mixture of dihydroxytetrahydrofuran regioisomers, methyl 9(12)-oxy-10,13-dihydroxystearate and methyl 10(13)-oxy-9,12-dihydroxystearate, was obtained from the hydrolyzed epoxide. These results show that untreated alumina is an unsuitable support for epoxidation catalysts. However, conversion of fats and oils and their derivatives to polyhydroxy materials may be desirable, as these materials are suitable for several industrial applications. Accordingly, an alumina-based epoxidation may be the most efficient way to achieve the synthesis of these polyhydroxy materials.