Insoluble Lignin Models (4): Condensation Reactions of a Polymer-Bound Guaiacylpropanol Model

The reactions of syringyl alcohol with itself and with either a soluble phenol, 3-methoxy-4-hydroxyphenylpropane (guaiacylpropane, 13) or an insoluble polymer-bound phenol, guaiacylpropanol (14) 1 , led to dimeric products. The low (11%), but significant yield of C5-Cα dimer 16 in the reaction of polymer-bound phenol with syringyl alcohol suggests that soluble lignin units are able to condense with insoluble lignin gels during the course of soda pulping. The yield of the C5-Cα dimer 15 in the soluble system was four times greater than that of the analogous heterogeneous dimer 16. Reactions of the polymer model 14 were not mass transfer limited.