Correlation of experimental and ab initio ~(13)C-NMR chemical shifts for monomeric lignin model compounds

摘要

The ~(13)C-NMR chemical shfits of monoemric model compounds representing the guaicyl,syringyl and -hydroxyphenyl forms of lignin were calculated using ab initio GIAO methods and compared to experimental data fromt he literature. The least squares regression analyses of the results indicate R-square values in excess of 0.96 for ht etotal dataset and upon sorting by compounds. Sorting by carobn position gave less accurate results with the chemical shifts for a given location dependent on the parent compound and environment of the carbon atom in question. The ability of a substituent group to rotate, and therefore to alter the geometry of the system, was particularly marked.