Silicon-29 NMR Spectral Studies of Kraft Lignin and Related Model Compounds

Abstract

Silicon-29 and carbon-13 NMR spectral data are presented for trimethylsilylated model compounds representing the structures like stilbenes, styryl aryl ethers, 5-and 6-condensed guaiacyl units, catechol rings, carbonyl structures, etc., which are expected in softwood kraft lignin. The data were used for the Interpretation of spectra of trimethylsilylated kraft lignin and kraft lignin derivatives. The spectra show a new view at the distribution of OH and COOH groups. Some Substitution effects on the silicon chemical shifts in the lignin structures are also discussed.