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Removal of phenolic hydroxyl groups in lignin model compounds and its effect on photostability

TitleRemoval of phenolic hydroxyl groups in lignin model compounds and its effect on photostability
Publication TypeJournal Article
Year of Publication2000
AuthorsHu, TQ, Cairns, GR, James, BR
JournalHolzforschung
Volume54
Pagination127-132
Type of ArticleArticle
ISBN Number0018-3830
KeywordsACETYLATION, DEGRADATION, DEOXYGENATION, GROUPS, HYDROGENATION, LIGNIN MODEL COMPOUNDS, METAL, METHYLATION, phenolic hydroxyl, photostability yellowing, REDUCTION
Abstract

The phenolic hydroxyl groups in the lignin model compounds, 2-methoxy-4-propylphenol and 4-hydroxy-3-methoxyacetophenone, were removed by first converting the hydroxyl groups to the trifluoromethanesulfonates (triflates) and then cleaving the triflate substituents via catalytic hydrogen transfer. The products, 1-methoxy-3-propylbenzene and 3-methoxyacelophenone: were characterized by H-1 and C-13 NMR, mass spectrometry and elemental analyses. The effect of the removal of the phenolic groups on the photostability of the model compounds was evaluated by impregnating the compounds into Whatman filter paper sheets, and subjecting them to an accelerated yellowing experiment in a UV chamber. The removal of the phenolic groups resulted in a significant yellowing inhibition, with a higher photostabilizing effect than methylation or acetylation of the hydroxyl, particularly for the model compound without an alpha-carbonyl group.

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