NMR studies of lignin models, derivatives and bleaching effluents
Abstract
NMR problems related to assignment techniques and relaxation restrict the use of
NMR in the structural analysis of lignin. These problems have been addressed in three
practical studies in this thesis involving a lignin model trimer and peroxide bleaching
effluents from spruce and investigation of correlation times of lignin using NMR
relaxation. Complete chemical shift assignments for aliphatic and aromatic protons and
carbons of a lignin model trimer were made using one- and two-dimensional NMR
experiments. Measurements from experiments using the nuclear Overhauser effect were
consistent with conformations of this model compound determined from semi-empirical
methods and the published experimental crystal structures of model dimers. Structures
present in the peroxide bleaching effluents of spruce ground wood were identified using
proton, phosphorus and COSY NMR experiments. Correlation times for acetylated kraft
lignin fractions varied between 2.7 x 10' s and 8.1 x 10' s when temperature, molecular
weight and concentration were changed. A greater concentration dependence was shown
for high mass samples.
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