Carbon 13C NMR Spectroscopy

Carbodiimides, 81 Carbodiimidization, 226-227 Carbon-13 NMR spectroscopy. See 13C NMR spectroscopy Carbon-carbon structure, 4 Carbonyl-containing polyester polyols,... 

On the other hand, 13C-NMR spectroscopy not only allows the simultaneous and separate detection of signals from different compounds, but also within different atoms in a given molecule. For example, carbon-13 from glucose labeled at the Cl (or C6) position is incorporated via the PDH reaction into the C2 of acetyl-CoA, and subsequently into the C4 of a-ketoglutarate (Fig. 31-9), which labels the... 

While many elements can be studied using NMR spectroscopy, only those elements at the top of the periodic chart are commonly measured by soil chemists, and of those, carbon-13 (13C) and phosphorus-31 (31P) are the most frequently investigated. Phosphorus is of particular interest because it is an essential nutrient for both plants and animals. 

Protonation of 4b leads to the symmetrically substituted 3b (Scheme 3.2-3) and methylation of 4b at temperatures higher than —60 °C gives 3c (Scheme 3.2-5) [19]. In the latter reaction, 6a can be identified as an intermediate at —80 °C by 13C NMR spectroscopy [19]. Its planar-tetracoordinate carbon atom is strongly de-shielded 3 13 C = 144 ppm) as compared with tetrahedrally-coordinated carbon atoms connected to three boron and one silicon center (d 13C = 70-100 ppm). Computations for the model compounds 6A and 6B give 144 and 104 ppm, re-... 

We pointed out in Section 13.3 that both H and 13C are nuclei that can provide useful structural information when studied by NMR. Although a H NMR spectrum helps us infer much about the carbon skeleton of a molecule, a 13C NMR spectrum has the obvious advantage of probing the carbon skeleton directly. 13C NMR spectroscopy is analogous to ll NMR in that the number of signals informs us about the number of different kinds of carbons, and their chemical shifts are related to particular chemical environments. 

NMR spectroscopy concerns radio frequency induced transitions between quantized energy states of magnetic nuclei that have been oriented by magnetic fields. Of these nuclei proton ( H) and carbon-13 (13C)... 

Nuclear magnetic resonance (NMR) spectroscopy (Section 14.1) A type of spectroscopy that uses transitions between the energy states of certain nuclei when they are in a magnetic field to supply information about the hydrocarbon part of a compound. There are two NMR techniques that are of most use to organic chemists proton magnetic resonance (lH-NMR) spectroscopy, which provides information about the hydrogens in a compound, and carbon-13 magnetic resonance spectroscopy (13C-NMR), which provides information about the carbons in a compound. 

With the exception of furopyridines, there have been no extensive studies using 13C NMR spectroscopy of these compounds. There is, however, a considerable volume of information concerning the, 3C NMR data for furopyridines <91JHC1469>. Table 23 lists l3C NMR data for the parent compounds and some simple derivatives. Based on analysis of the 13C NMR data, the C-2 and C-3 shifts are very similar to those for furan, indicating that the fused pyridine ring has minimal electronic effect upon those carbon atoms. Carbon-13 NMR data for a series of furodipyridines... 

The olefin polymerization catalyst based on Cp2TiCl13CH3/B(C6F5)3 has been studied by varying solvent polarity and catalyst concentration. Reaction equilibria and polymerization with carbon-13 enriched ethylene have been studied by 13C NMR spectroscopy.1216... 

The carbon-skeleton has been viewed directly with the help of Carbon-13 NMR spectroscopy on a particle basis since early 1970 s whereas -NMR spectrometry started in late 1950 s. The valuable contribution made by various researchers, between 1976 and 1980, has virtually placed 13C-NMR to a strategically much advanced stage where it gives a clear edge over 1H-NMR in terms of not only its versatility but also its wide application in analysis. 

The epoxidation reaction was monitored by high performance liquid chromatograph (HPCL) on a reverse phase column. The reaction product was identified by IR, proton NMR and carbon-13 NMR spectroscopy. In the IR spectrum, absorption bands at 904 cm-1 and 842 cm-1 were attributed to the epoxy groups (12) peaks at 2.60, 2.78, and 3.15 ppm on the 1H-NMR spectrum were assigned to the three protons of the epoxide group (13) and in the 13C-NMR spectrum, the three glycidyl carbons were identified at 44.5, 50.6, and 70.6 ppm (14). 

C NMR (Section 13.14) Nuclear magnetic resonance spectroscopy in which the environments of individual carbon atoms are examined via their mass 13 isotope. 

Schaefer J, Stejskal EO (1979) High-resolution 13C NMR of solid polymers, in Levy GC (ed) Topics in Carbon-13 NMR spectroscopy, Wiley, New York, vol 3... 

In future, the methods of two-dimensional NMR spectroscopy (Section 2.10) will be the ones used for the unequivocal signal identifications of longer chain peptides. Complete 13C shift assignments are achieved from carbon-proton shift correlations via two- and three-bond couplings, as is demonstrated for the orange-red chromopeptide antibiotic actinomycin D (Fig. 5.13, Table 5.28, [603, 812]). 

The classic text on 13C NMR is G. C. Levy, R. L. Lichter, and G. L. Nelson, Carbon-13 Nuclear Magnetic Resonance Spectroscopy, 2nd ed., Wiley Interscience, New York, 1980. 

Solid-state NMR spectroscopy is arguably the most commonly applied NMR technique in the study of NOM structure because whole soil or sediment analysis can be performed without sample extraction. The 13C nucleus is typically the focus of NOM solid-state NMR studies because strong 1H-1H dipolar interactions (which cannot be easily overcome experimentally) in the solid state result in extremely broad lines. However, because the natural abundance of the 13C isotope is only -1.13% of the total carbon present, observing 13C signals directly is often difficult. 

We speculate that process changes could cause changes in sequence distribution. C NMR spectroscopy has been used to study similar copolymers (10,11,12) and hence should be of value in correlating process with sequence distribution, nmr is a means of looking at changes in the electronic environment of nucleii of the isotope of carbon, 13C. There are a number of texts on % NMR spectroscopy and its application to organic molecules, and polymers (13,14,15). The chemical shifts which one observes as characteristic of different carbons can be caused by... 

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