The Isomeric Compositions of Monohydroperoxides Produced by Oxidation of Unsaturated Fatty Acid Esters With Singlet Oxygen

The isomeric compositions of monohydroperoxides produced by oxidation of unsaturated fatty acid esters with chemically produced singlet molecular oxygen were determined by mass chromatography as the trimethylsilyl derivatives of hydroxy-octadecanoate. Methyl oleate formed equal amounts of the 9- and 10-isomers. Methyl linoleate formed equal amounts of the four isomeric hydroperoxides, the 9-, 10-, 12- and 13-isomers. Six isomers, the 9-, 10-, 12-, 13-, 15- and 16-isomers, were obtained from the monohydroperoxides of methyl linolenate in which the quantities of the 9- and 16- isomers were slightly higher than those of other isomers. The isomeric compositions of monohydroperoxides obtained by chlorophyll sensitized photooxidation were very similar to those formed by chemically produced singlet oxygen except that the proportions of the 9- and 13-isomers were higher than those of the 10- and 12-isomers in methyl linoleate.