The Structure and Conformation of Lignin as Judged by X-ray Crystallographic Investigations of Lignin Model Compounds: Arylglycerol β-Syringyl Ethers

Paper in proceeding, 2008

Structural elements of the arylglycerol β-syringyl ether type are very frequent in hardwood lignins. A variety of crystalline dimeric lignin models representing different diastereomeric forms of structural elements in lignin of this type have been studied using X-ray crystallography. Bond distances and bond angles in the model compounds are in all probability nearly identical with those of the corresponding structural elements in lignins. Based on X-ray crystallographic data from four compounds a sequence of units (5 aromatic rings, 8 chiral Catoms) attached to each other by β-syringyl ether linkages was constructed. The appearance of the resulting oligomer illustrates that stereoisomerism can be expected to influence the shape of the lignin molecules to a great extent. The constructed oligomer constitutes one of 256 possible stereoisomers (128 racemates).