Substituent effects on carbon-13 chemical shifts of aromatic carbons in β-O-4 and β-5 type lignin model compounds.

ABSTRACT Substituent effects on the chemical shifts of aromatic carbons in lignin model compounds have been elucidated from C NMR spectra of guaiacyl and syringyl type monomerio and β-O-4 model compounds and guaiacyl type β-5 model compounds. Evaluation of the observed values of substituent chemical shift (SCS) for the aromatic carbons leads to elucidation of a generalized SCS additivity rule,…