Bleaching of vegetable oils. II. Conversions of methyl oleate and linoleate

Methyl oleate and linoleate were treated with 10% acid activated clay at 90–100 C for 1–50 hr with and without admission of air. Positional and geometric isomers of fatty acid esters were found. Polar compounds were detected having one or more functional groups with respect to the starting esters. Preparative thin layer chromatography and gas liquid chromatography were used in isolating the compounds, while IR, NMR, mass spectroscopy, and gas liquid chromatography analysis were employed for identification. The unsaturation of the isolated isomers was present at carbon atoms 5–11. The polar compounds were, among others, 9- and 10-keto octadecanoic methyl esters, isomeric keto octadecenoic methyl esters, isomeric epoxy octadecanoic methyl esters, 9- and 10-hydroxy octadecanoic methyl esters, and some mono methyl ester dicarbonic acids. It may be concluded that geometric, as well as positional, isomerization occurs and that small amounts of compounds with one or more functional groups are formed when unsaturated fatty acids were treated with acid-activated clay.