Reactions of lignin with cyanamide activated hydrogen peroxide Part 2. The degradation mechanism of phenolic lignin model compounds

The reactions of monomeric phenolic lignin model compounds with cyanamide activated hydrogen peroxide were studied. Analyses of the various reaction products indicate four main reactions occur; aromatic hydroxylation, demethoxylation, radical coupling and oxidative ring opening. The predominate products from apocynol and acetoguaiacone were dicarboxylic acid compounds, maleic/fumaric, oxalic, and succinic acid derivatives, consistent with degradation by superoxide. In the degradation of creosol, 3-hydroxy-4-methoxy-6-methyl-N-methylaniline was the major compound is elated, providing evidence of a cyanamide radical. Finally, plausible pathways to the formation of superoxide anion and cyanamide oxidation products from alkaline hydrogen peroxide and cyanamide are proposed and their impact on delignification is discussed.