[C-13] NUCLEAR MAGNETIC-RESONANCE SPECTRUM OF A METHYLATED HUMIC-ACID

A humic acid has been investigated by [13C]NMR spectroscopy using the methylated humic acid dissolved in chloroform which gave a relatively simple spectrum. Estimates of different types of C show that 21% of the C is aromatic, 35% consists of methylene chains and methyl groups, 3%, as the carbonyl C of methyl esters, and 13% as the methoxyl C of methylated phenols and alcohols. The rest, 28%, is not accounted for and may be mostly C bound to O as in polysaccharides or in peptides. No ketonic or quinonic groups were detected. The [13C]NMR spectrum of the methylated humic acid is entirely different from those of lignin and its derivatives thus suggesting that lignin residues play no significant role in the structure of the humic acid. © 1979.