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

Abstract

Summary 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.

Review of the bulk and surface chemistry of iron in atmospherically relevant systems containing humic-like substances

“…The presence of the -OCH 3 group as a substituent on the benzene ring, as in the case of guaiacol, favours the formation of oligomers at the expense of stable guaiacol-Fe complexes. 138 The addition of iron results in the development of soluble amber-coloured (about 412 and 470 nm) dimers and trimers of guaiacol. These have also been observed by Hwang et al 139 from the biochemical oxidation of guaiacol by manganese peroxidase in the presence of H 2 O 2 .…”

Modification of the Wood Surface Properties of Tsoongiodendron odorum Chun with Silicon Dioxide by a Sol-gel Method

“…Many methods have been used to improve the surface properties of wood, namely wood dyeing, wood bleaching, wood painting, wood preservation, surface strengthening, surface chemical decoration, plasma polymerization, surface activation, etc. (Schmalzl et al 1995;Podgorski et al 2002;Rehn et al 2003;Fu et al 2012). For wood samples, moisture absorption on the surface of wood has serious impact on dimensional stability.…”

Enhancing Weathering Resistance of Wood—A Review

“…Ferric chloride was shown to provide some resistance against natural weathering and restricted colonization by stain fungi [ 123 ]. However, Evans and Schmalzl [ 129 ] reported that ferric salts were ineffective in reducing weathering probably because no formation of stable, weather resistant lignin–metal complexes occurred [ 127 , 130 ]. Titanates (tetrabutyl, tetraisopropyl, and ethylhexyl titanate) and zirconates (tetrapropyl and tetrabutyl zirconate) are colourless, but have also been shown to be unable to protect lignin from photodegradation during natural weathering [ 122 ].…”