Solid-State 13C NMR (Nuclear Magnetic Resonance) Determination of the Syringyl/Guaicyl Ratio in Hardwood

摘要

The unprotonated aromatic regions of the solid-state 13C NMR spectra of several hardwoods and softwoods are examined. Spectra are acquired with cross polarization, magic-angle spinning, and delayed proton decoupling. The hardwood spectra are decomposed into syringyl and guaiacyl components with the aid of a softwood spectrum, which is assumed to be the same as the guaiacyl component of the hardwood spectrum. The molar ratio of syringylpropanoid units to guaiacylpropanoid units (S/G) in hardwood is determined from the intensities of their respective component spectra. These results were comparable to literature values that were obtained by a combination of methoxyl and elemental analyses.