Use of beta-C-13 labelled coniferyl alcohol to detect end-wise polymerization in the formation of DHPs

The possibility that preformed dehydrogenation polymer (DHP) could function as a template to induce a structural pattern in DHP more closely resembling that of natural softwood lignin was investigated by oxidizing beta C-13-labelled coniferyl alcohol in a medium containing preformed unlabelled polymeric DHP. The experiments were performed at pH 4 and pH 6.5. 1D and 2D NMR were used to estimate the distribution of structural units. No such template effect was found in a comparison of unlabelled with uniformly labelled DHP. Indeed, the effect of pH on the coupling pattern of coniferyl alcohol was geater than the effect of the preformed DHP.