A procedure is described demonstrating the formation of four hydroperoxide isomers in the autoxidation of methyl oleate in accordance with the free radical chain reaction concept of autoxidation. Experimental proof is also given for the location of the hydroperoxide group in the a-position relative to the double bonds. New methodology is reported in the use of catalytic reduction with the Lindlar Catalyst for the quantitative estimation of peroxides, The quasi-six membered ring theory of oxidation as applied to the atmospheric oxidation of fats is shown to have no factual basis.
Struktur-Untersuchung und Analyse der bei der Autoxydation von Methyloleat entstehenden Hydroperoxyd-Isomeren Vf. beschreibt ein Verfahren, da8 die Bildung von vier Hydroperoxyd-Isomeren bei der Autoxydation von Methyloleat in Ubereinstimmung mit dem Radikalmechanismus -wie er bei der Autoxydation angenommen wirddemonstriert. Ein experimenteller Beweis fur den a-Methylenmechanismus der Autoxydation wird gebracht; uber eine neue Methodik zur quantitativen Bestimmung der Peroxyde mittels der katalytischen Reduktion mit Iiilfe des Lindlar-Katalysators wird berichtet. Die durchgefuhrten Untersuchungen zeigen, da8 die 6-Ringtheorie der Autoxydation nicht bewiesen werden kann. Determinacih de fa estructura y andlisis de 10s isomeros hidroperoxidos de metil oleatos autoxidados El autor describe un procedimiento que demuestra la forma-ci6n de cuatro isomeros hidroperoxidos por la autoxidacion del metil oleato en concordancia con el mecdnismo-radical coma el ha aceptado para la autoxidacion. Se comprueba experimenlalinente par el mecanismo de metilacion la autoxidacion; se According to the hydroperoxide theory '. four monomeric monoethenoid hydroperoxyide isomers should be formed in equal proportions in the autoxidation of methyl oleate.
J.
Ross, A . J. Gebhart and J . F. Gerecht2 obtained qualitative evidence for the formation of four hydroperoxy isomers and suggested that the relative proportions of each isomer was 10)11)8)9. It was pointed out, however, that some selective fractionation may have occurred by the procedure employed for the analysis.
Application of the same technique by N. T. SZover and L. R. Dujail j r . '' to the radiation induced autoxidation of methyl oleate also indicated that four isomers were formed. The proportions in this case for the 8, 9, 10 and 11 isomers were 1.9 and 6 ' / o , 7.8 and 9.6 "10, 56.0 and 59.6'Io. and 34.0 and 2-1.9Oiu respectively on two runs performed under slightly different conditions.
H . B. Knight, C. R. Eddy and D . S w e m 4 suggested that the 9 and 10 hydroperoxy isomers were formed preferentially on the basis of the finding of predominately the high melting 9.10-dihydroxystearic acid and low melting 9,10-epoxystearic acid in autoxidized oleie acid.
'' Work supported by the Hormel Foundation.