C NMR Spectroscopy of Organic Compounds

Silverstein, R.M. and G.C. Basler, Spectrometric Identification of Organic Compounds, New York Wiley, 1968. Jackman, L.M. and S. Stemhell, Applications of NMR Spectroscopy in Organic Chemistry, London, Pergamon Press, 1969. 

The chemical shift of a nucleus reflects the molecular structure and it can therefore be used to obtain structural information. Further, as hydrogen and carbon (and therefore iR and nuclei) are universal constituents of organic compounds the amount of structural information available from H and C NMR spectroscopy greatly exceeds in value the information available from other forms of molecular spectroscopy. 

Because of the small but consistent concentrations of present in all organic compounds, it is necessary to use more sophisticated NMR spectroscopy for determining the effect of neighboring electrons on these nuclei. However, C-NMR spectroscopy is a valuable tool for investigating polymer structure. 

Nitrenium cation is an extremely unstable species (89-91). That is why nitrenium complexes are usually prepared by the interaction of organic compounds with some sources of nitrenium cation (91, 92). Thus, the interaction of O-mesityl-sulfonylhydroxylamine with 1,10-phenanthroline results in the formation of l-amino-l,iO-phenanthrolinium mesitylenesulfonate (93-99). The structure of this salt has been confirmed by H and C NMR spectroscopy (93,... 

Early studies involved pyrolysis of this residue and revealed the presence of aromatic ring systems such as benzene, naphthalene, their alkyl derivatives as well as higher aromatic hydrocarbons. Today, GC-MS analyses of super-critical fluid extracts of hydrous pyrolysates (77), Ha-pyrolysis products (72) as well as solid-state C-NMR spectroscopy (75) of meteorite organic residues are applied to provide insight into the structure of the macromolecular carbon. Most recent, hydrothermal treatment (300 °C at 10 MPa) of demineralized lOM of the Murray meteorite has yielded in the release of a wide variety of carboxylic acids and heteroaromatic compounds including C3-C17 alkyl carboxylic acids and N-, O-and S-containing hydroaromatic and aromatic compounds (74). 

NMR spectroscopy was developed by physical chemists in the late 1940s to study the properties of atomic nuclei. In 1951, chemists realized that NMR spectroscopy could also be used to determine the structures of organic compounds. We have seen that electrons are charged, spinning particles with two allowed spin states +1/2 and — 1/2 (Section 1.2). Certain nuclei also have allowed spin states of +1/2 and —1/2, and this property allows them to be studied by NMR. Examples of such nuclei are H, C, F, and... 

An application of FTIR and C NMR spectroscopy on hydrothermal coalification could determine the decomposition of organic compounds in peat at different treated temperature. Increasing the temperature of the hydrothermal treatment resulted in an increase in relative area intensity of the aromatic carbons bound to the hydrogen (Ar-H), aromatic non-oxygenated carbon (Ar-C) and aromatic oxygenated carbon (Ar-O). These mean and also correspond to the increasing of aromaticity as well as coalification degree. 

The low frequency of the NMR active isotope in organic compounds (1.1% in comparison to the isotope) means that a relatively high amount of substance is necessary for the C-NMR experiment. If only a small amount of substances is available, H-NMR measurements are possible [209] but the nuclear resonance separations are much smaller than in C-NMR spectroscopy. The H-NMR measurements permit quantification ofmelhylene units contained in the products [33]. 

Volume 88 of Annual Reports on NMR Spectroscopy begins with Reviewing 47/49 i i Solid-State NMR Spectroscopy From Alloys and Simple Compounds to Catalysts and Porous Materials by B.E.G. Lucier and Y. Huang this is followed by an account on Advances in Al MAS NMR Studies of Geopolymers by J. Brus, S. Abbrent, L. Kobera, M. Urbanova, and P. Cuba Applications of NMR Techniques in the Development and Operation of Proton Exchange Membrane Fuel Cells are covered by L. Yan, Y. Hu, X. Zhang, and B. Yue K. Damodaran presents a report on Recent NMR Studies of Ionic Liquids Recent SoHd-State C NMR Studies of Liquid Crystals are reviewed by K. Yamada the volume concludes with an account of A Toolbox of Solid-State NMR Experiments for the Characterization of Soft Organic Nanomaterials by L.A. Straaso, Q. Saleem, and M.R. Hansen. 

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