PREPARATIVE SEPARATION AND H-1-NMR IDENTI FICATION OF PRODUCTS OF LINOLEIC-ACID AUTOOXIDATION

Bulk phase oxidation of linoleic acid in a diffuse system in the dark at 2 - 5 degrees C was found to produce three types of oxygenated deri vatives. An effective method of HPLC on the nitrile phase was develope d for the analysis and preparative isolation of products, which made i t possible to prepare individual structural isomers of each type. Afte r preliminary identification by chemical, chromatographic, and UV spec troscopic methods, the isolated compounds were identified as 9- and 13 -isomers of hydroperoxy-, hydroxy-, and ketooctadecadienoic acids with Z-E-conjugated double bond systems. The formation of minor E-E-regioi somers of linoleic acid hydroperoxides was also observed. The assignme nt of signals in the H-1 NMR spectra of the compounds isolated, includ ing homonuclear proton-decoupled spectra, validated the proposed struc tures. It is suggested that the preferable formation of Z-E-isomers of oxygenated products in the process of linoleic acid autooxidation tin der low temperature is connected with impossibility of overcoming the energy barrier of primary peroxyradical isomerization.