ORGANOTELLURIUM COMPOUNDS AS EFFICIENT RETARDERS OF LIPID-PEROXIDATION IN METHANOL

Diaryl tellurides were found efficiently to retard ate-initiated lipid peroxidation of linoleic acid in methanol. The most efficient compoun ds, 31 and 39, contained one and two hydroxyl groups, respectively, in the para positions and methyl groups in all four positions ortho to t ellurium. As determined by the values of n . k(inh) these materials we re as effective retarders of lipid peroxidation as vitamin E. Contrary to the conventional antioxidants examined, diaryl tellurides were fou nd to inhibit peroxidation for long times, seemingly with an autocatal ytic mechanism. Diaryl tellurides were found to be partially oxidized during the peroxidation. The reduction of tellurium (IV) compounds to the divalent state during the conditions of the experiment is discusse d. The reactivity of some diaryl chalcogenides toward 2,2-diphenyl-1-p icrylhydrazyl (DPPH) in methanol was studied. All compounds investigat ed were less reactive than vitamin E. One of the most active organotel lurium compounds, bis(4-aminophenyl) telluride, reacted considerably f aster with DPPH than the corresponding selenide or sulfide. It was con cluded that mechanisms involving both hydrogen atom transfer and elect ron transfer were operative in the reaction of organotellurides with D PPH.