Nuclear magnetic resonance aliphatic proton resonances

Nuclear Magnetic Resonance. The nmr spectmm of aromatic amines shows resonance attributable to the N—H protons and the protons of any A/-alkyl substituents that are present. The N—H protons usually absorb in the 5 3.6—4.7 range. The position of the resonance peak varies with the concentration of the amine and the nature of the solvent employed. In aromatic amines, the resonance associated with N—CH protons occurs near 5 3.0, somewhat further downfield than those in the aliphatic amines. 

Carborane, Bk>C2Hi2, is quite soluble in aromatic solvents and is sparingly soluble in aliphatic solvents. The infrared spectrum has been previously reported.25 The proton nuclear magnetic resonance spectrum of a chloroform-d3 solution of carborane contains a broad CH resonance at 6.46 t. 

Fulvic and humic acids have been investigated with carbon-13 and proton nuclear magnetic resonance spectrometry, GC/MS, and IR spectroscopy. The fulvic and humic acids were found to be predominantly carboxylic and aromatic with a high proportion of 0- and Ji-substituted carbon atoms, although aliphatic ones were also observed. 

Several methods are available in the literature for the measurement of aliphatic amines in biological samples [28]. Problems with specificity and separation and cumbersome derivatisation and/or extraction procedures have limited the use of these techniques on a larger scale in clinical practice. The lack of a simple analytical method may have led to an underestimation of the incidence of the fish odour syndrome. For diagnosing the syndrome, an analytical technique should be used that is able to simultaneously and quantitatively measure TMA and its N-oxide in the complex matrix of human urine. Two such methods are currently available for this purpose proton nuclear magnetic resonance (NMR) spectroscopy and head-space gas analysis with gas chromatography or direct mass spectrometry (see below). 

Greenzaid, P., Z. Luz, and D. Samuel A Nuclear Magnetic Resonance Study of the Reversible Hydration of Aliphatic Aldehydes and Ketones. I. Oxygen-17 and Proton Spectra and Equilibrium Constants. J. Am. Chem. Soc. 89, 749 (1967). 

The study of humic substances by nuclear magnetic resonance of the isotope and the proton suggests that aliphatic structures prevail over aromatic structures for the fulvic acids extracted from marine water, contrary to the case for soil fulvic acids. The high values of the H C ratio in marine fulvic acids also point to an aliphatic nature (Stuermer and Payne, 1976). 

Fischer H, Gyllenhaal O, Vessmann J, Albert K (2003) Reaction monitming of aliphatic amines in supercritical carbon dioxide by proton nuclear magnetic resonance spectroscopy and implications for supercritical fluid chromatography. Anal Chem 75 622-626... 

Nuclear magnetic resonance spectrometry has solved so many problems that one would hope it could be applied to the determination of aliphatic weak bases. Taft and Levins (338) have succeeded in using this method through the effect of protonation on the fluorine resonance of several p-fluorinated bases. Unfortunately, the flu-orinated aromatic system is required and also a relatively concentrated solution of indicator so that the use of aqueous acid is ruled out. In acetic-sulfuric acid solutions Taft finds serious medium effects for Hammett indicators but sharp titration curves for car-bonium ion bases. This result is in complete agreement with the conclusions described previously (II-D) for solvation of carbonium ions compared to other onium ions. 

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