Saturated carbons, protons attached

In saturated systems, the magnitude of the geminal coupling constant h-c-h (two protons attached to the same carbon atom) is typically between 10 and 16 Hz but values between 0 and 22 Hz have been recorded in some unusual structures. 

In the NMR spectrum of the irradiated acetate we notice a strong modification of the olefinic region. The integrated spectrum shows that the total number of the olefinic protons has decreased while the number of protons attached to saturated carbons increases. This loss of olefinic protons led us to think that dimerization had occurred. The mass spectrometry enabled us to confirm this hypothesis. ... 

We shall start with protons on saturated carbon atoms. If you study Table 11.1 you will see that the protons in a methyl group are shifted more and more as the atom attached to them gets more electronegative. 

For effective spin-lattice relaxation, the tumbling magnetic nuclei must be spatially close to the resonating nucleus. For attached protons provide effective spin-lattice relaxation. A carbonyl carbon or a carbon attached to four other carbons thus relaxes very slowly and is more easily saturated because the attached atoms are nonmagnetic ( C and... 

The organic phases from the extraction of uranyl sulphate solutions (0, 5 and 100 g/1) containing sulphuric acid with 0.1 M TOPO in carbon tetrachloride at 20 °C were examined by NMR spectroscopy. The NMR spectrum of water-saturated TOPO solution shows a peak at 9.11 (t value) in a triplet due to the methyl protons, a sharp peak at 8.68 arising from methylene protons, and a peak at 5.53 from methylenic protons attached to a phosphorous atom, and the water proton signal at 7.58, indicating the formation of the compound TOPO- O. In the organic solutions from the extraction of... 

The NMR spectra of several dihydro-1,3,5-triazines have been reported.247,258-263,266-270 Since most of the known compounds of this type bear either aromatic, polychloroalkyl, or polyfluoroalkyl substituents on the triazine ring, H NMR is used for the former and 19F NMR for the latter derivatives. The main information obtained from H NMR concerns the NH and H or alkyl substituents on the sp3 carbon. Thus the NH signals of tautomeric 1,2- and 1,4-dihydro-l,3,5-triazines were found in the region <5 5.1-8.2 in CDC13 and 5 8.0-11.0 in DMSO-d6. The downfield shift of the NH signal in DMSO is caused by intermolecular hydrogen bonds formed between the polar solvent and the solute. Similar to the situation in the dihydropyrimidines, the NH signal of the 1,4-dihydro isomer appears at a lower field than that of the 1,2-dihydro isomer. The proton attached to the saturated... 

The double and triple resonance experiments with roxburghine-D establish that the hydrogen atom at 0-15 Hg) is coupled to two hydrogens at C-14 and one at C-20 but there is also a small coupling between Hb and the hydrogen atom (H2) at C-17 (t/ 15,17 = 0.6 Hz). Such an allylic coupling is reasonable on the basis of structure 80 but is much less easily rationalized on the basis of structure 81. Further, the chemical shifts observed for the protons at C-15 and C-20 (S 2.15 and 1.76, respectively) are consistent with an allylic position for the former and an attachment of C-20 to saturated carbon atoms only. 

The resonance range of protons attached to a saturated ring carbon atom is at higher field, as would be expected for aminal-type protons there are two reports on signals at even higher field which do not conform with this assignment (Table 3). 

The n.m.r. spectra of coccinellin and precoccinellin exhibit a doublet owing to a methyl group attached to a saturated carbon atom. No olefinic protons are present, and since coccinellin gives no other evidence of unsaturation it must be tricyclic. Precoccinellin affords a methiodide which exhibits, in addition to the N-Me signal, a complex 3H absorption at 4.17 p.p.m., indicating the presence in the free base of only three protons on carbon atoms adjacent to the tertiary nitrogen atom. 

Cholesterol (Fig. 1.20) is a steroid, the same rigid five-ring backbone used for the mammalian sex hormones. There are only two functional groups an olefin (C-5, C-6) and an alcohol (C-3). The bulk of the molecule can be described as saturated hydrocarbon. There are five methyl groups two are attached to quaternary carbons so they should appear as singlets and three are attached to CH carbons so they should appear as doublets. Most of the protons in the A, B, and C rings can be described as axial or equatorial due to the rigid,... 

The number of incorporated D atoms and their positions led to the conclusion that the proton of formic acid attacks the enamine / -carbon by a reversible process (which would explain incorporation of more than 1 D per molecule). Then the hydride derived from the formate becomes attached to the iminium carbon to give the saturated amine. 

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