Chemical shielding effect

However, because of chemical shielding anisotropy (CSA) and quadnipolar and dipolar effects, the Lamior... 

FIG. 10 Plots of AGt ° " (z-dep)/w against E (with r = rjj) for hydrated cations (O) and anions ( ). Note that the n values for the plots of Ca and Ba + have been corrected for the shielding effect (see text) by subtracting 4 from their net values of n (X) represents the plots with the net values. Solid lines show the regression curves [Eqs. (45) and (46)]. (From Ref. 49. Copyright 1998 American Chemical Society.)... 

Amino groups have a shielding effect on chemical shift similar to that of an OH group (Scheme 4.28). 

H and 13C NMR Data. A ketone or aldehyde carbonyl group bound to a CF2H group shields its proton slightly (0.1 ppm), and even more surprisingly, it also has a shielding effect upon its carbon chemical... 

Note too from the chemical shifts of these methyl groups that tin has quite a strong shielding effect. 

This shows that the second and further solvation shells still have a non-negligible effect on NMR chemical shielding constants through the long-range electrical field they create. The approximation of an isolated molecular cluster in vacuo is valid for large clusters only this eventually makes determination of the shieldings of all protons computationally much more expensive than the fully periodic ab initio calculation. 

For the CH with a Cs symmetrical structure 1 a 13C NMR chemical shift of 11.5 ppm is calculated. This is 7.1 ppm more shielded than that calculated for the hydrocarbon CH4 at the GIAO-MP2 level.19 The shielding effect in 1 is as expected for a hypercoordinated carbocation carbon.20 The calculated minimum energy structure for diprotonated methane (CHi+) 2 has C2v symmetry with two 3c-2e... 

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