Related Experiment Video
Updated: Sep 10, 2026

Extraction of Lignin with High β-O-4 Content by Mild Ethanol Extraction and Its Effect on the Depolymerization Yield
Published on: January 7, 2019
Photostabilizing milled wood lignin with benzotriazoles and hindered nitroxide
1Department of Chemistry, McGill University, Pulp and Paper Research Center, 3420 University Street, Montreal, Quebec, Canada H3A 2A7.
Abstract:
The inhibitory processes operating when a 2(-2'-hydroxyphenyl) benzotriazole-based ultraviolet absorber (UVA) and a hindered nitroxide free radical are applied to high-yield pulps were studied using milled wood lignin and filter paper as a model. Using quantitative 31P NMR it was determined that the UVA is almost completely photostable during irradiation, suggesting that its protective mechanism is based primarily on ultraviolet absorption. Furthermore, the nitroxide was found to protect the UVA from photodegradation. Analysis of irradiated lignin samples involved derivatization followed by reductive cleavage of beta-arylether groups. The phenolic-OH groups thus released were quantified using 31P NMR. The benzotriazole/nitroxide stabilizing system was found to cooperatively inhibit the cleavage of beta-arylether groups. Furthermore, this system was found to have a synergistic inhibitory effect on the formation of catechol structures. These results suggest that the synergism observed between benzotriazole-based UV screens and nitroxyl radicals on the inhibition of yellowing could be a result of their ability to slow the formation of catechol structures and beta-O-4 cleavage in addition to the possibility of a UVA-regeneration mechanism.
Related Concept Videos
Reactions at the Benzylic Position: Oxidation and Reduction
Electrophilic Aromatic Substitution: Nitration of Benzene
meta-Directing Deactivators: –NO2, –CN, –CHO, –⁠CO2R, –COR, –CO2H
Directing and Steric Effects in Disubstituted Benzene Derivatives
Radical Oxidation of Allylic and Benzylic Alcohols

