Alkaline cupric oxide oxidation of a methylated fulvic acid

Abstract

Fulvic acid, (FA), extracted from the Bh horizon of a Podzol soil, was methylated and then oxidized with alkaline cupric oxide. The oxidation products were extracted into organic solvents, remethylated and separated by column-, thin layer-, and preparative gas chromatography into relatively pure components, which were identified by matching their mass and i.r. spectra and gas Chromatographic retention times with those of authentic specimens. The degradation products isolated and identified accounted for approximately 18 per cent of the weight of the initial methylated FA. Major oxidation products were: (a) methylated phenolic aldehydes and esters (66.9 per cent): (b) benzenecarboxylic acid methyl esters (14.6 per cent): (c) aliphatic dicarboxylic acid methyl esters (2.7 per cent): and (d) adsorbed materials such as n-alkanes (0.3 per cent), n-fatty acid methyl esters (0.3 per cent) and dioetyl adipate (15.2 per cent). The oxidalive degradation of methylated FA indicates the presence of two types of basic structural units: (1) those yielding phenolic aldehydes and esters, and (2) those producing benzenecarboxylic acids. Alkaline cupric oxide oxidation of methylated FA is relatively selective for the isolation of the phenolic components and appears to be a promising technique for structural investigations on humic substances.