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Methylation patterns of aquatic humic substances determined by 13C NMR spectroscopy

Organic Geochemistry

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, , and

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Abstract

13C NMR spectroscopy is used to examine the hydroxyl group functionality of a series of humic and fulvic acids from different aquatic environments. Samples first are methylated with 13C-labeled diazomethane. The NMR spectra of the diazomethylated samples allow one to distinguish between methyl esters of carboxylic acids, methyl ethers of phenolic hydroxyls, and methyl ethers of phenolic hydroxyls adjacent to two substituents. Samples are then permethylated with 13C-labeled methyl iodide/NaH. 13C NMR spectra of permethylated samples show that a significant fraction of the hydroxyl groups is not methylated with diazomethane alone. In these spectra methyl ethers of carbohydrate and aliphatic hydroxyls overlap with methyl ethers of phenolic hydroxyls. Side reactions of the methyltion procedure including carbon methylation in the CH3I/NaH procedure, are also examined. Humic and fulvic acids from bog, swamp, groundwater, and lake waters showssome differences in their distribution of hydroxyl groups, mainly in the concentrations of phenolic hydroxyls, which may be attributed to their different biogeochemical origins. ?? 1987.

Additional Publication Details

Publication type:
Article
Publication Subtype:
Journal Article
Title:
Methylation patterns of aquatic humic substances determined by 13C NMR spectroscopy
Series title:
Organic Geochemistry
Volume
11
Issue:
3
Year Published:
1987
Language:
English
Larger Work Type:
Article
Larger Work Subtype:
Journal Article
Larger Work Title:
Organic Geochemistry
First page:
123
Last page:
137
Number of Pages:
15