Comprehensive study on the chemical structure of dioxane lignin from plantation Eucalyptus globulus wood.
Results of a comprehensive study on the chemical structure of lignin from plantation Eucalyptus globulus Labill are presented. Lignin has been isolated by a modified mild acidolysis method and thoroughly characterized by functional group analysis, by a series of degradation techniques (nitrobenzene oxidation, permanganate oxidation, thioacidolysis, and Py-GC-MS), and (1)H and (13)C NMR spectroscopy. Plantation Eucalyptus globulus lignin was found to be of the S/G type with an extremely high proportion of syringyl (S) units (82-86%) and a minor proportion of p-hydrophenyl propane (H) units (roughly 2-3 mol %). Unknown C-6 substituted and 4-O-5' type syringyl substructures represent about 65% of lignin "condensed" structures. Eucalypt lignin showed high abundance of beta-O-4 (0.56/C(6)) structures and units linked by alpha-O-4 bonds (0.23/C(6)). The proportion of phenylcoumaran structures was relatively low (0.03/C(6)). Different kinds of beta-beta substructures (pino-/syringaresinol and isotaxiresinol types) in a total amount of 0.13/C(6) were detected. ESI-MS analysis revealed a wide molecular weight distribution of lignin with the center of gravity of mass distribution around 2500 u.
Evtuguin
D V
DV
Department of Chemistry, University of Aveiro, 3810 Aveiro, Portugal. dmitry@dq.ua.pt
Neto
C P
CP
Silva
A M
AM
Domingues
P M
PM
Amado
F M
FM
Robert
D
D
Faix
O
O
D004146:Dioxanes; D005052:Eucalyptus / Q000737:chemistry*; D008401:Gas Chromatography-Mass Spectrometry; D008031:Lignin / Q000032:analysis / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy; D015394:Molecular Structure; D008970:Molecular Weight; D010946:Plants, Medicinal; D021241:Spectrometry, Mass, Electrospray Ionization
D004146:Dioxanes; D008031:Lignin