The Syringyl Content of Softwood Lignin

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Abstract
Representations of softwood lignins typically include small amounts, 2 to 5%, of syringylpropane units. Carbon-13 nuclear magnetic resonance and pyrolysisgas chromatography of loblolly pine milled wood lignin indicated a much lower value. Pyrolysis-gas chromatography/mass spectrometry of whole softwoods also gave lower than expected yields of syringyl products. One chemical method, alkaline nitrobenzene oxidation, was also used to determine syringyl content. Results obtained using these methods indicate that the syringyl content of lignin in typical softwoods appears to be less than 0.1% of the total phenylpropane units. Ginkgo was also examined, and its lignin was found to contain only a very small amount of syringylpropane units. Cambial extracts of three softwoods were analyzed by pyrolysis-gas chromatography/mass spectrometry, and the data indicated the possibility of the presence of a slight amount of syringin. These results suggest that lignin in typical softwoods is formed almost exclusively from coniferyl alcohol.