- Author
- Manders, W. F.
- Title
- Solid-State (13)C NMR Determination of the Syringyl/Guaiacyl Ratio in Hardwood.
- Coporate
- National Bureau of Standards, Gaithersburg, MD
- Report
- NBSIR 86-3380, May 1986, 22 p.
- Distribution
- Available from National Technical Information Service
- Keywords
- carbon 13 | guaiacyl | hardwood | lignin | nuclear magnetic resonance | softwood | magic angle spinning | syringyl | cross polarization
- Abstract
- The unprotonated aromatic regions of the solid-state (13)C 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. Ratios for elm (0.45), basswood (0.70), oak (0.70), maple (0.85), cherry (1.00), birch (1.00), and poplar (1.20) are reported. These results were comparable to literature values that were obtained by a combination of methoxyl and elemental analyses. Nitrobenzene oxidation gave syringaldehyde/vanillin ratios that were approximately three times greater than the corresponding NMR S/G ratios.