THE REACTION OF GUAIACOL WITH IRON-III AND CHROMIUM-VI COMPOUNDS AS AMODEL FOR WOOD SURFACE MODIFICATION

The reaction of ferric chloride with the lignin model guaiacol affords primarily a complex mixture of coupled guaiacol oligomers. Major comp onents were the symmetrical carbon-carbon coupled dimer 3,3'-dimethoxy -[1,1'-biphenyl]-4,4'-diol and the trimer 3,3'',5'-trimethoxy- [1,1':3 ',1''-terphenyl]-4,4',4''-triol which were isolated by preparative HPL C and characterized by H-1 NMR spectroscopy and mass spectrometry. An unstable component believed to be a 4,4'-diphenoquinone derived from t he trimer was also prominent. The reaction of chromium trioxide with g uaiacol yields the same dimer, trimer and diphenoquinone as well as 2- methoxy-p-benzoquinone. The major product with chromium trioxide, howe ver, is an inert, highly insoluble polymer which was shown by degradat ion to contain guaiacol oligomers bound or crosslinked by hydroxylated chromium species. Magnetic susceptibility measurements clearly indica ted that the valency of chromium in the polymer was +3. It is postulat ed that similar complexes formed from phenolic lignin units are respon sible for the weather resistance of chromium trioxide treated wood sur faces. In a broader context this study is relevant to the fixation of hexavalent chromium from a range of widely used wood preservative form ulations.