Hydrogen nuclear magnetic resonance spectroscopy

Most aldohexopyranoses exist in a chair form in which the hydroxymethyl group at C(5) assumes an equatorial position. All the P-D-hexopyranoses exist predominantly in the 4Ci form since the alternative C4 conformer involves a large unfavourable xyn-diaxial interaction between the hydroxymethyl and anomeric group (Figure 1.8). Most of the a-D-hexopyranosides also adopt the 4Ci conformation preferentially. Only ot-idopyranoside and a-D-altropyranose show a tendency to exist in the C4 conformation, and they coexist with the alternative 4Ci conformations according to H-NMR (hydrogen nuclear magnetic resonance) spectroscopy studies. 

Bottomley PA (1987) Spatial localization in NMR spectroscopy in vivo. Ann NY Acad Sci 508 333-348 Bottomley PA, Edelstein WA, Foster TH, Adams WA (1985) In vivo solvent-suppressed localized hydrogen nuclear magnetic resonance spectroscopy a window to metabolism Proc Natl Acad Sci USA 82 2148-2152 Brown TR, Kincaid BM, Ugurbil K (1982) NMR chemical shift imaging in three dimensions. Proc Natl Acad Sci USA 79 3523-3526... 

Hydroboration-oxidation, 227-233, 250, 582 Hydroformylation, 661, 732 Hydrogen. See also Hydrogenation Nuclear magnetic resonance spectroscopy covalent bonding in, 12 formation of, 6 molecular orbitals, 34-35 nuclear spin states, 490-491 Hydrogenation. See also Heat of... 

We saw in Chapter 12 that mass spectrometry gives a molecule s formula and infrared spectroscopy identifies a molecule s functional groups. Nuclear magnetic resonance spectroscopy does not replace either of these techniques rather, it complements them by "mapping" a molecule s carbon-hydrogen framework. Taken together, mass spectrometry, JR, and NMR make it possible to determine the structures of even very complex molecules. 

Nuclear Magnetic Resonance Spectroscopy in Homogeneous Hydrogenation Research... 

NUCLEAR MAGNETIC RESONANCE SPECTROSCOPY HYDROGEN NUCLEI... 

Although Eibner elucidated the structure between 1904 and 1906, it was only through IR and nuclear magnetic resonance spectroscopy (NMR) that the chro-maticity of these molecules could be attributed to keto-enol tautomerism and simultaneous hydrogen bond formation (structures 137a = 137b) [2]. 

Nuclear magnetic resonance spectroscopy has been developed as a standard method for the determination of hydrogen types in aviation turbine fuels (ASTM D3701). X-ray fluorescence spectrometry has been applied to the determination of lead in gasoline (ASTM D2599) as well as to the determination of sulfur in various petroleum products (ASTM D2622, D4294). 

Low-resolution nuclear magnetic resonance spectroscopy can also be used to determine percent by weight hydrogen in jet fuel (ASTM D3701) and in light distillate, middle distillate, and gas-oil (ASTM D4808). As noted above, chromatographic methods are not applicable to naphtha, where losses can occur by evaporation. 

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