Shielding of nuclei in NMR spectroscopy

Sex hormones, 1040—1042, 1044 Shared-electron pair bond. See Covalent bond Shielding of nuclei in NMR spectroscopy, 493—495. See also Chemical shift Sickle-cell anemia, 1089—1090, 1100 Sigma bond, 32... 

In the opening chapter, An Introduction to Solution, Solid-State, and Imaging NMR Spectroscopy Leslie Butler (Louisiana State University) introduces the fundamental structure parameters in the NMR experiment through a discussion on solution state H NMR. The shielding of nuclei by core and valence electrons, gives rise to those structure-pregnant numbers called chemical shifts, d, that have been accrued and correlated since the earliest days of NMR. Scalar coupling,... 

Figure 16 Spectral lineshapes for powdered solids. (A) Peak doublet produced by dipole coupling between two spin 1/2 nuclei. The doublet is composed of two parts (shown dotted). They correspond to the observed proton flip occurring when its neighbor is spin up (left) or spin down (right). The indicated turning points correspond to the angle between the internuclear vector and 5b. (B) Chemical shift anisotropy pattern with shielding tensor components (Til, < 22. and (T33. (C) Combined DD and CSA spectrum. Note that this is not simply (A) -1- (B). (Reproduced with permission from Power WP and Wasylishen RE (1991) In Webb GA (ed.) Annual Reports in NMR Spectroscopy, vol. 23, p. 17. London Academic Press.)...

The most important magnetic property by far is the chemical shift of NMR spectroscopy. While proton H) and 13C shieldings hold a prominent place in organic chemistry, other magnetic nuclei such as 15N, 29Si, or 31P but also heavier nuclei such as transition-metals are increasingly important in many areas of chemistry. Obviously, all these nuclei are equally... 

A different class of phenomena can be related to the interaction of the electronic polarization density and induced current with the nuclei. Thus the chemical shifts in nuclear magnetic resonance (NMR) spectroscopy are interpreted in terms of magnetic shielding of the electrons, perturbed by a static magnetic field, at those nuclei possessing an intrinsic magnetic moment [7]. 

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