OXIDATION OF BETA-O-4 LIGNIN MODEL DIMERS BY H2O2 CATALYZED BY COPPER PHENANTHROLINE

摘要

This work aims at elucidating some of the key steps of the oxidation pathways of lignin model compounds using Cu(II)-phenantroline as catalyst and hydrogen peroxide as oxidant. Phenolic and non-phenolic betaO-4 dimeric phenyl propane structures were selected as lignin models since they represent the most abundant structures in lignin. The compounds used in this work are not commercially available; therefore all of them were synthesized. Oxidation reactions were carried out under alkaline conditions, at 80 °C for 3 h. The lignin model dimer (LMD) disappearance and some of the oxidation products were identified by HPLC analyses. Products as acetaldehyde, veratric or vanillic acid, and guaiacol were identified as resultant products of LMD oxidations. A tentative mechanism which involves the oxidation of the benzylic alcohol group followed by the cleavage of the beta-ether linkages is proposed.