General Tendency of Lignin Chemical Structure and its Relation to Reactivity

Hardwood lignins are different from softwood lignins by the presence of syringyl type aromatic nuclei. In addition, there are wide varieties in the structure and amount of hardwood lignins depending on wood species, environment of growing site, portion in the wood, portion in the cell wall, and so on. We have shown that the wide variety of lignin structure and amount can be sorted out by taking the syringyl/guaiacyl ratio as an index. Furthermore, we have also shown that lignin structure can be quantitatively related to the chemical reactivity such as delignification during chemical pulping by taking the syringyl/guaiacyl ratio as an index. In this report, we review our recent achievements about the quantitative relationships between lignin structure and reactivity.