Incorporation of Chlorinated Anilines into Lignin

Abstract

Abstract Coniferyl Alcohol, Peroxidase, Lignin, 4-Chloroaniline, 3,4-Dichloroaniline Lignin was formed in vitro by the peroxidase/hydrogen peroxide mediated polymerization of coniferyl alcohol. In the presence of [14C]4-chloroaniline or [14C]3,4-dichloroaniline copolymeri­ zation occurred with incorporation rates of about 45 mol%. Co-elution of UV-absorbing material (reflecting lignin) and of incorporated radioactivity was observed on a calibrated column of Sephadex LH-60. This method indicated a broad molecular weight distribution of the copolymers with values of between about 20000 and 1000. Most of the copolymer products had apparent molecular weights near 1000. The 1H-NMR and 13C-NMR spectra of the copolymers were compared with those of in vitro lignin. The copolymer spectra showed a relative increase in aromatic peaks and a relative decrease in most of the typical lignin peaks. Three peaks indicative of a new type of phenyl-propanoid side-chain structure were detected in the 'H-NMR and 13C-NMR spectra of the copolymers. The corresponding 1H-NMR chemical shift values were 4.75 ppm (a-C-H), 4.40 ppm (β-C-H) and 3.70/3.50 ppm (y-C-H2). The 13C-NMR chemical shift values were 56.9 ppm (a-C), 84.3 ppm (β-C) and 60.0 ppm (y-C). These peaks were attributed to a 3-aryl-3-anilino-2-aryloxy-propanol-1 structure in the copolymers by analysis of coupling patterns and by comparison with spectral reference data. The NMR-results and experiments with catalase and inhibitors suggested that a major mechanism of copolymerization consisted of a nucleophilic addition of the anilines to the benzylic ar-carbon of lignol quinone-methide intermediates.