NMR STRUCTURAL INVESTIGATIONS OF AQUATIC HUMIC SUBSTANCES (PYRAZOLINE, 1,3-DIPOLAR ADDITION, NITROGEN-15).
type: CreativeWork
description: The hydroxyl group functionality of a series of aquatic humic and fulvic acids was examined by methylating the samples with ¹³C-enriched reagents and looking at the ¹³C NMR of the resulting methyl esters and ethers. The methylation procedure entailed methylation with ¹³C-diazomethane followed by permethylation with ¹³C-methyl iodide/sodium hydride, DMF the solvent in both steps. The ¹³C NMR of diazomethylated samples allows one to distinguish between carboxylic acid OH, phenolic OH, and phenolic OH adjacent to two substituents. The ¹³C NMR spectra of permethylated samples shows that a significant amount of the hydroxyl group functionality can be methylated only when a strong base is used. The sources of the aquatic humic substances investigated included groundwater, lake, bog, and swamp waters. The ¹³C NMR spectra of the permethylated humic and fulvic acids revealed that the total hydroxyl group pattern--carboxylic acid OH, carbohydrate OH, phenolic and aliphatic OH--was very similar among these aquatic samples despite the fact that they represented biogeochemically different sources. Practical applications of this ¹³C NMR characterization technique are briefly illustrated. These include following the chemical changes in the Spirit Lake fulvic acid following the eruption of Mt. St. Helens, analyzing the chromatographic fractionation of a groundwater fulvic acid, and analyzing the residual products after chlorination of two commercial humic acids. Side reactions of the methylation procedure were also studied. A ¹⁵N NMR investigation of the 1,3 dipolar addition of diazomethane to a soil fulvic acid led to the tentative conclusion that the cycloadduct was an N-methyl pyrazoline. Evidence is presented that carbon methylation occurs to a large extent during the CH₃I/NaH step. The derivatization of ketone and/or quinone groups with methoxylamine for the purpose of viewing these groups as the N-OCH₄ derivatives in the ¹³C NMR was also examined. Solid state CP/MAS ¹³C NMR s…
abstract: The hydroxyl group functionality of a series of aquatic humic and fulvic acids was examined by methylating the samples with ¹³C-enriched reagents and looking at the ¹³C NMR of the resulting methyl esters and ethers. The methylation procedure entailed methylation with ¹³C-diazomethane followed by permethylation with ¹³C-methyl iodide/sodium hydride, DMF the solvent in both steps. The ¹³C NMR of diazomethylated samples allows one to distinguish between carboxylic acid OH, phenolic OH, and phenolic OH adjacent to two substituents. The ¹³C NMR spectra of permethylated samples shows that a significant amount of the hydroxyl group functionality can be methylated only when a strong base is used. The sources of the aquatic humic substances investigated included groundwater, lake, bog, and swamp waters. The ¹³C NMR spectra of the permethylated humic and fulvic acids revealed that the total hydroxyl group pattern--carboxylic acid OH, carbohydrate OH, phenolic and aliphatic OH--was very similar among these aquatic samples despite the fact that they represented biogeochemically different sources. Practical applications of this ¹³C NMR characterization technique are briefly illustrated. These include following the chemical changes in the Spirit Lake fulvic acid following the eruption of Mt. St. Helens, analyzing the chromatographic fractionation of a groundwater fulvic acid, and analyzing the residual products after chlorination of two commercial humic acids. Side reactions of the methylation procedure were also studied. A ¹⁵N NMR investigation of the 1,3 dipolar addition of diazomethane to a soil fulvic acid led to the tentative conclusion that the cycloadduct was an N-methyl pyrazoline. Evidence is presented that carbon methylation occurs to a large extent during the CH₃I/NaH step. The derivatization of ketone and/or quinone groups with methoxylamine for the purpose of viewing these groups as the N-OCH₄ derivatives in the ¹³C NMR was also examined. Solid state CP/MAS ¹³C NMR s…
author: THORN, KEVIN ARTHUR.
language: en
keywords: Humates., Humates -- Analysis., Humates -- Spectra., Nuclear magnetic resonance.
date published: 1984
date modified: 2026-07-24T00:57:45Z
provider: University of Arizona
publisher: Networked Digital Library of Theses and Dissertations
type: WebPage
source organization: The University of Arizona.

PropertyValue
property ID: Handle
value: http://hdl.handle.net/10150/187665