Formation of peroxides in fatty esters. II. Methyl linoleate: application of the polarographic and direct oxygen methods

Summary This study of the prolonged autoxidation of methyllinoleate at 80°C. has included polarographic identification and determination of hydroperoxides, the direct determination of oxygen contents, and catalytic micro-hydrogenation for the determination of unsaturation. The polarographic method has further substantiated the observations of other workers that the principal peroxidic substance formed during the autoxidation of methyl linoleate at 80°C. is a hydroperoxide. The direct oxygen measurements have shown that most of the oxygen absorbed in the initial stages of autoxidation can be accounted for as hydroperoxide. During the latter stages there was a continuous increase of oxygen uptake, half of which can be accounted for as free acid and half as forms other than hydroperoxide, ester, or free acid. By means of the catalytic micro-hydrogenation method it has further been shown that as the autoxidation progresses there is a continuous decrease in unsaturation.