One-bond proton—carbon coupling constant

The two axes (dimensions) in our 2D spectra are thus both frequency axes. We shall see as we continue that we can adjust our experiment so as to choose different types of frequency information. An early experiment, known as the J-resolved experiment, was designed in such a way that one axis was the (proton or carbon) chemical shift axis and the other the one-bond proton-carbon coupling constant. Flowever, this experiment is not generally very useful for structural determination, so that we shall not discuss it here. 

Table 4.2. Typically ranges for one-bond proton-carbon coupling constants...

S. Uhrinova, D. Uhrin, T. Liptaj, J. Bella, J. Hirsch, Measurement of one-bond proton-carbon coupling constants of saccharides, Magn. Reson. Chem. 29 (1991) 912-922. 

H and 13C NMR Data. Pertinent proton and carbon NMR data, in addition to those given above, are provided in Scheme 3.9. Again, the increase in one-bond F—C coupling constant observed in the... 

Proton and carbon NMR data for these multi-CF3-substituted benzenes are provided in Schemes 5.53 and 5.54. Individual one-bond F-C coupling constant data are not provided because virtually all of these coupling constants are in between 272 and 276 Hz. 

The pH-dependencies of one-bond C-C coupling constants in a number of amino acids have been reported by Tran-Dinh et al. (57, 58) Each carbon in the amino acids was uniformly enriched to 85%. The values of lJ(C0-Ca) are similar to those observed in aliphatic carboxylic acids. In the zwitterion, lJ(C0-Ca) values lie between 53-4 and 54-1 Hz upon protonation of the carboxyl group this coupling constant increases by about 6 Hz. 

C(8) and C(5), C(ll) respectively, can be correlated with the one-bond C,H coupling constants via the proton shifts. This assignment of the J(C,H) coupling constants will be confirmed, as shown in Sect. 4, by vicinal C,H coupling constants between the N-methyl carbon and the diastereotopic methylene protons. When the observed J(C,H) values are compared with the reference data for the non-cyclic glycyl peptides it is evident that the rather large value of 150.0 Hz deserves special attention. 

T.N. Pham, T. Liptaj, K. Bromek, D. Uhrin, Measmement of small one-bond proton-carbon residual dipolar coupling constants in partially oriented C natmal abundance oligosaccharide samples. Analysis of heteronuclear JcH-modulated spectra with the BIRD inversion pulse, J. Magn. Reson. 157 (2002) 200—209. 

Organophosphorus compounds rarely have more than one P atom in the molecule, giving rise to a doublet for any C atom within three bonds (assuming the proton-carbon coupling has been removed) and so these compounds show clearly the connectivity of carbon atoms close to the P atom. The size of the coupling constant is dependent on the number of bonds and the phosphorus oxidation state, such that Vis the largest at about 45-150 Hz, while V and V are of the order of 10-15 Hz. 

The proton and carbon NMR spectra of 2,2,3,3,3-pentafluoro-propylamine are given in Figures 6.14 and 6.15. In its proton spectrum, one sees the triplet at 3.22 ppm due to the CH2 group, with its three-bond F-H coupling constant of 15.5 Hz. 

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