The Synthesis and Chemical Structures of Tetrameric Lignin Model Compounds

In order to study the reaction of high molecular weight residual lignin in pulp with chlorine dioxide, three types of tetrameric lignin model compounds were designed and synthesized. All three tetramers contain diphenylmethane condensation - type structures but 1 also contains a biphenyl structure and 3 contains β-arylether linkages. Synthesis of tetramer 1 involved oxidative coupling of vanillin followed by reduction and condensation with an excess of creosol under alkaline conditions. Tetramer 2 was prepared by the condensation of vanillin with formaldehyde followed by reduction and condensation as for tetramer 1. Preparation of tetramer 3 was accomplished by condensation of a dimer containing a β-aryl ether linkage with formaldehyde.