Three quarters of the western red cedar's heartwood colour is due to a polymeric material easily isolated by methanol extraction. The nature of this polymer has not been fully investigated and published information is contradictory. Our initial examination of the coloured polymer by pyrolysis-gas chromatography, combined with mass spectrometry, indicated that the polymer was guaiacyl in nature and thus similar to softwood lignin. However, analysis by infrared spectroscopy indicated the presence of both lignin and lignan like moieties. To clarify this issue a more detailed analysis was conducted using nuclear magnetic resonance spectroscopy ( 1 H NMR, 31 P NMR, 13 C NMR). Analysis of the spectra and comparison with the spectra of plicatic acid and a product from mild acid treatment of plicatic acid, indicated that the polymeric fraction was derived almost entirely from lignans. During polymer formation, the highly reactive pyrocatechol moiety in the plicatic acid is destroyed, leaving a guaiacyl-like polymer.The reaction mechanism appears to proceed via an ortho-quinone intermediate followed by polymerization.

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Identification of the three chromophores provides a basis for studies of the kinetics of brightening of western red cedar mechanical pulps.

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The use of western red cedar mechanical pulp is limited by its very low brightness. This article presents the kinetic expressions for hydrogen peroxide brightening of western red cedar chemimechanical pulp. The significance of the results for the reaction mechanism and for brightening under practical conditions is discussed. The kinetics of peroxide brightening of western red cedar chemimechanical pulp was monitored at the three absorption maxima-357 nm, 457 nm, and 550 nm-in the UV-visible spectra. The reaction order with respect to hydrogen peroxide was around 1 at all three wavelengths. The reaction order with respect to chromophores was approximately 2.4 at the higher wavelengths and 5 at 357 nm. The kinetic equations were successful in predicting brightness values obtained under practical conditions.