title: Milled wood lignin: a linear oligomer.
abstract: The degree of polymerization (DP) of softwood and hardwood milled wood lignin samples and their branching degrees were quantitatively evaluated by a novel end-group titration approach composed of QQ-HSQC, (31)P NMR, and DFRC coupled with (31)P NMR analysis techniques. The DP of lignin can be calculated when the C9 formula, the amounts of phenolic groups, pinoresinol (β-β), diphenylethane (β-1), and phenolic diphenyl (5-5') lignin subunits have been determined. Data on the degree of polymerization of lignin obtained by NMR techniques were not affected by supramolecular aggregation processes. (31)P NMR analysis coupled with DFRC and QQ-HSQC allowed a detailed evaluation of the occurrence of condensed units in lignin and showed the terminal nature of diphenyl ether and diphenyl subunits. The resulting data unequivocally show that milled wood lignin is a linear oligomer.
authors.affiliation: Dipartimento di Scienze e Tecnologie Chimiche, Tor Vergata University, Via della Ricerca Scientifica, 00133, Rome, Italy. crestini@stc.uniroma2.it
authors.forename: Claudia
authors.initials: C
authors.lastname: Crestini
authors.forename: Federica
authors.initials: F
authors.lastname: Melone
authors.forename: Marco
authors.initials: M
authors.lastname: Sette
authors.forename: Raffaele
authors.initials: R
authors.lastname: Saladino
mesh_terms: D000107:Acetylation; D029964:Fagus / Q000737:chemistry; D008031:Lignin / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy; D008970:Molecular Weight; D010084:Oxidation-Reduction; D010636:Phenols / Q000737:chemistry; D028222:Picea / Q000737:chemistry; D015238:Sulfotransferases; D014934:Wood / Q000737:chemistry*; D000097811:Carbohydrate Sulfotransferases
chemical_list: D008031:Lignin; D010636:Phenols; D015238:Sulfotransferases; D000097811:Carbohydrate Sulfotransferases