The reaction of guaiacol with iron III and chromium VI compounds as a model for wood surface modification

✍ Scribed by K. J. Schmalzl; C. M. Forsyth; P. D. Evans

• Book ID: 104661479
• Publisher: Springer
• Year: 1995
• Tongue: English
• Weight: 831 KB
• Volume: 29
• Category: Article
• ISSN: 0043-7719
• DOI: 10.1007/bf00202090

✦ Synopsis

The reaction of ferric chloride with the lignin model guaiacol affords primarily a complex mixture of coupled guaiacol oligomers. Major components were the symmetrical carbon-carbon coupled dimer 3,Y-dimethoxy-[1,1'-biphenyl]-4,4'diol and the trimer 3,Y',5'-trimethoxy-[1,1':Y, l"-terphenyl]-4,4',4"-triol which were isolated by preparative HPLC and characterized by 1HNMR spectroscopy and mass spectrometry. An unstable component believed to be a 4,4'-diphenoquinone derived from the trimer was also prominent. The reaction of chromium trioxide with guaiacol yields the same dimer, trimer and diphenoquinone as well as 2-methoxy-p-benzoquinone. The major product with chromium trioxide, however, is an inert, highly insoluble polymer which was shown by degradation to contain guaiacol oligomers bound or crosslinked by hydroxylated chromium species. Magnetic susceptibility measurements clearly indicated that the valency of chromium in the polymer was + 3. It is postulated that similar complexes formed from phenolic lignin units are responsible for the weather resistance of chromium trioxide treated wood surfaces. In a broader context this study is relevant to the fixation of hexavalent chromium from a range of widely used wood preservative formulations.