Carbon-13 nuclear magnetic resonance identification

Other spectroscopic methods such as infrared (ir), and nuclear magnetic resonance (nmr), circular dichroism (cd), and mass spectrometry (ms) are invaluable tools for identification and stmcture elucidation. Nmr spectroscopy allows for geometric assignment of the carbon—carbon double bonds, as well as relative stereochemistry of ring substituents. These spectroscopic methods coupled with traditional chemical derivatization techniques provide the framework by which new carotenoids are identified and characterized (16,17). 

Vervoort, J., et al. (1986). Identification of the true carbon-13 nuclear magnetic resonance spectrum of the stable intermediate II in bacterial luciferase. Biochemistry 25 8062-8067. 

In an attempt to delineate the degree of preservation of lignin in pre-Tertiary coal, we examined numerous coalified wood samples ranging in age from Carboniferous to Cretaceous. The samples were initially screened by solid-state l C nuclear magnetic resonance to detect the possible presence of methoxyl carbon. Once such carbons were detected, the samples were subjected to analytical pyrolysis to determine the relative yields of methoxyphenols which would provide an indication of the state of preservation of the lignin-derived structu units. We report here on the identification of lignin-derived methoxyphenols in the coalified wood samples selected for analytical pyrolysis. 

Infrared (IR), carbon-13 nuclear magnetic resonance ( C NMR), and proton NMR ( H NMR) spectroscopy provide diagnostic resonances for the identification... 

Several spectroscopic techniques, namely, Ultraviolet-Visible Spectroscopy (UV-Vis), Infrared (IR), Nuclear Magnetic Resonance (NMR), etc., have been used for understanding the mechanism of solvent-extraction processes and identification of extracted species. Berthon et al. reviewed the use of NMR techniques in solvent-extraction studies for monoamides, malonamides, picolinamides, and TBP (116, 117). NMR spectroscopy was used as a tool to identify the structural parameters that control selectivity and efficiency of extraction of metal ions. 13C NMR relaxation-time data were used to determine the distances between the carbon atoms of the monoamide ligands and the actinides centers. The II, 2H, and 13C NMR spectra analysis of the solvent organic phases indicated malonamide dimer formation at low concentrations. However, at higher ligand concentrations, micelle formation was observed. NMR studies were also used to understand nitric acid extraction mechanisms. Before obtaining conformational information from 13C relaxation times, the stoichiometries of the... 

Figure 15.9. 13C CPMAS NMR spectrum of humin extracted from a brown chernozem soil from Western Canada. The characteristic doublet in the unsubstituted aliphatic region is characteristic of methylene carbon (28-34 ppm) and shows the presence of both amorphous (soft) domains at 29 ppm and crystalline (rigid) domains at 33 ppm in soil humin. Reprinted from Simpson, M. I, and Johnson, R C. E. (2006). Identification of mobile aliphatic sorptive domains in soil humin by solid-state 13C nuclear magnetic resonance. Environ. Toxi. Chem. 25, 52-57, with permission from the Society of Environmental Toxicology and Chemistry.

Kalchhauser H, Robien W. CSEARCH a computer program for identification of organic compounds and fully automated assignment of carbon-13 nuclear magnetic resonance spectra. J Chem Inf Comput Sci 1985 25 103-108. 

Oldfield, E., and Allerhand, A. (1975)./. Amer. Chem. Soc. 97, 221. Identification of Tryptophan Resonances in Natural Abundance Carbon-13 Nuclear Magnetic Resonance Spectra of Proteins. Application of Partially Relaxed Fourier Transform Spectroscopy. 

Most of the development work on molecular markers (MMs) has resulted from the use of GC-MS, but with advances in other techniques it is clear that this field will benefit from making greater use of alternative identification methods, such as Fourier transform infrared spectroscopy and nuclear magnetic resonance techniques. Isotopic measurements can now be used to obtain complimentary information on the history and origin of a sample. It is now possible to perform a forensic investigation using stable carbon isotopic analyses on individual MMs by GC-Isotope Ratio MS without prior isolation of com-... 

Brekke, T., Barth, T., Kvalheim, O. M. and Sletten, E. (1990) Multivariate analysis of carbon-13 nuclear magnetic resonance spectra. Identification and quantification of average structures in petroleum distillates. Analytical Chemistry, 62, 56-61. 

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