H-1 AND C-13 NMR-STUDY OF LIGNIN STRUCTUR E

A comparative analysis of the chemical structure of lignin from aspen milled wood (Bjorkman lignin), aspen dioxanlignin, and lignin from exp loded aspen wood was performed by method of H-1 and C-13 NMR spectrosc opy. In is found that a more rigid mechanical method of the lignin iso lation from wood causes oxidation of the side chains to C=O, C(O)H and C(O)OH groups, cleavage of the aryl-alkyl ether bonds with the format ion of phenolic hydroxyl groups, rupture of the ester bonds, and conde nsation reactions between macromolecules. In addition, the C-C bonds o f the side chains are cleaved with the detachment of alkyl OH groups. The chemical structure of dioxanlignin is modified to such a considera ble extent that it is difficult to consider this structure as similar to that of lignin obtained from aspen milled wood. The structure of li gnin from explosive aspen wood is similar to that of milled wood ligni n only with respect to the ratio of fragments of syringyl, guaiacyl an d p-hydroxyphenyl fragments.