C-13 NMR CHARACTERIZATION OF GUAIACYL, GUAIACYL SYRINGYL AND SYRINGYLDEHYDROGENATION POLYMERS/

Dehydrogenation polymers (DHPs) were prepared from coniferyl alcohol ( CA), sinapyl alcohol (SA), and a mixture of coniferyl and sinapyl alco hol. The polymers were fully acetylated and their carbon NMR spectra w ere compared. Comparison of the C-13 NMR spectra of the DHPs with thos e of authentic tri-and tetralignols facilitated the assignment of abou t 85 % of the 117 reported signals. Most of the unassigned signals wer e those from syringyl units. Major differences between the DHP prepare d from CA and a pine milled wood lignin were: a relative deficiency of beta-O-4 linkages and a predominance of beta-5, beta-beta, and CA end units in the DHP. In contrast, there was no significant quantity of S A end units in a DHP prepared from SA. A major conclusion of the study confirmed that DHPs prepared from CA are relatively poor models of na tural lignins isolated from gymnosperms.