APPLICATION OF 2-DIMENSIONAL NMR-SPECTROSCOPY TO WOOD LIGNIN STRUCTURE DETERMINATION AND IDENTIFICATION OF SOME MINOR STRUCTURAL UNITS OF HARDWOOD AND SOFTWOOD LIGNINS

Two-dimensional NMR techniques, homonuclear Hartmann-Hahn (HOHAHA), and H-1-detected multiple quantum H-1-C-13 correlation spectroscopy were applied to hard- and softwood milled wood Lignin (MWL) samples. The structural units of MWLs were found to be very similar to those of released suspension culture Lignin, but the MWL samples contained diarylpropane-1,3-diol units, which have now been identified unambiguously for the first time in lignin samples. Correlations which may arise from arylpropane-1,3-diol 2-aryl ether structures etherified in the 3-position were also observed. Furthermore, some not yet identified structures have been detected, as well as novel structural differences between hard- and softwood lignins.