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This paper presents a complete structural investigation into the main extracted lignin of Quercus robur and Q. petraea heartwood. Extensive 1H and 13C homo- and heteronuclear NMR were employed, particularly the TOCSY and HMQC techniques. Three major fractions represented the raw material: lignan, the most degradative form of lignin polymers, the ethanol-lignins which are very similar to the lignins obtained during ageing spirits on wood contact and finally the dioxan-lignin, almost similar to the in situ lignins. All these fractions were characterized as syringyl–guaiacyl structures with mainly β-O-4 and β–β linkages. S/G ratio was 1.1 and 2.7, for ethanol-lignin and dioxan-lignin, respectively. The lignan fraction required a second step of purification to obtain two lignans (60:40, w/w) prior to NMR investigation, in order to obtain preliminary structural information. To cite this article: N. Vivas et al., C. R. Chimie 9 (2006). |
