A structural investigation on the main fraction of dimers formed during the induction period of autoxidation in methyl linoleate (ML) was carried out. The dimeric fraction (A2), which was isolated from the autoxidized ML (POV = 18) by various chromatographic techniques and gave a single spot on TLC, was further separated into four major components (components 1-4) by high performance liquid chromatography (HPLC). The mean molecular weights of these components were found to be 643 - 655 and component 4 gave the parent peak 652 on an FD-mass spectrum which corresponded to 2×ML + 4O. The reduced products of each component with stannous chloride were identified in common as methyl 9- or 13-hydroxy octadecadienoate and methyl 9, 13-dihydroxy octadecenoate by GC-MS. These results show that all of these dimers contained a peroxide bridge linking between a pair of MLs across C-9 or C-13 on one of the MLs and C-9 or C-13 on the other, with a hydroperoxy group.
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Miyashita et al. (1982) studied this question.