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Lundquist, K., and Parkås, J. (2011). "Different types of phenolic units in lignins," BioRes. 6(2), 920-926.

Abstract

The influence of cross-linking and branching on the number of interconnections between lignin units and the number of end groups (phenolic and non-phenolic) in the lignin molecules is discussed. Branching results in an increased number of end groups. It appears from an evaluation of the literature that p-hydroxyphenylpropane units are phenolic to a larger extent than guaiacylpropane units and that such units in turn are phenolic to a larger extent than syringylpropane units. It is proposed that this is related to the relative oxidation potentials of the lignin units. Guaiacylpropane units C-substituted in the 6-position are phenolic to a large extent. Alternative explanations for this are presented.
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