FREE-RADICALS PRODUCED BY THE OXIDATION OF COMPOUNDS CONTAINING SYRINGYL AND GUAIACYL GROUPS

Compounds containing syringyl or guaiacyl groups were oxidized with O- 2, O-2(-), H2O2, or hexacyanoferrate (III) at pH 13, and their electro n spin resonance (ESR) spectra were measured, The two kinds of radical s observed by the oxidation of dioxane lignins from various plants wer e identified to be 2,6-dimethoxy-p-benzosemiquinone and 5-hydroxy-2-me thoxy-p-benzosemiquinone radical anions, Demethoxylation was observed when syringaldehyde, syringic acid or vanillic acid were oxidized with hexacyanoferrate (III). Acetovanillon, vanillylaicohol, o-methoxy-phe nol, guaiacyl glycerol-beta-guaiacyl ether and syringyl glycerol-beta- guaiacyl ether did not give stable radicals by their oxidation, The pr oduction mechanism of the two kinds of radicals observed in ESR by the oxidation of dioxane lignins is discussed.