The DFRC Method for Lignin Analysis. 2. Monomers from Isolated Lignins

Monomers released from derivatization followed by reductive cleavage (DFRC degradation) of lignins have been identified by mass spectra and/or comparison of their GC retention times with authentic compounds. The primary monomers from several isolated lignins representing softwoods, hardwoods, grasses, and dicots have been quantified by GC. Sources of the minor monomeric components have been rationalized on the basis of the DFRC mechanisms; products from cinnamyl alcohol endgroups, aldehydes, arylglycerols, and α-carbonyl units have been identified. From isolated lignins, the DFRC method produces its diagnostic primary monomers, the hydroxycinnamyl peracetates, with yields comparable to the production of monomers from other ether-cleaving analytical methods. Keywords: Acetyl bromide; lignin; β-aryl ether; thioacidolysis; β-bromoether; quantitative analysis; reductive elimination; DFRC