Chemical shift correlations hydrogen

HETCOR (Section 13 19) A 2D NMR technique that correlates the H chemical shift of a proton to the chemical shift of the carbon to which it is attached HETCOR stands for heteronuclear chemical shift correlation Heteroatom (Section 1 7) An atom in an organic molecule that IS neither carbon nor hydrogen Heterocyclic compound (Section 3 15) Cyclic compound in which one or more of the atoms in the nng are elements other than carbon Heterocyclic compounds may or may not be aromatic... 

Carbon-13 chemical shifts of the a- and (8-carbon atoms of various unsubstituted and 3-substituted thietane oxides and dioxides have been recorded and correlated by the equations S = ay + bx and Sf = ax + by where a and b are parameters characteristic of the sulfoxide or sulfone (y) and the substituent (x)216. The values of the substituent parameters were found to parallel those which determine the effect on the 13C chemical shifts when hydrogen is replaced by a substituent224. 

Ionic dissociation of carbon-carbon a-bonds in hydrocarbons and the formation of authentic hydrocarbon salts, 30, 173 Ionization potentials, 4, 31 Ion-pairing effects in carbanion reactions, 15, 153 Ions, organic, charge density-NMR chemical shift correlations, 11,125 Isomerization, permutational, of pentavalent phosphorus compounds, 9, 25 Isotope effects, hydrogen, in aromatic substitution reactions, 2,163... 

NMR spectra of solids, and thus soil, are obtained by what is called magic angle spinning. The spectra obtained have broader absorption features than NMR spectra of components in solution or liquids. Numerous NMR experiments such as 3H—13C heteronuclear chemical shift correlation (HETCOR), which identifies which hydrogen atoms are attached to which carbon atoms, can also be carried out on solid samples. A great deal of useful information about the structure of components in soil can thus be obtained from NMR investigations [5,6],... 

With more than 100 elements besides carbon in the periodic table (Appendix 2), you might fear that the number of H chemical shift correlations is endless. However, except for a few specialized applications, the most important heteroatoms to which hydrogen finds itself bonded are oxygen and nitrogen. But before we discuss these two specific cases, here is a useful generalization As the electronegativity (Table 6.1) of X increases, both the acidity and chemical shift of a hydrogen bonded directly to X increase. 

Figure 7.3. Graphical comparison of H chemical shifts of C-H hydrogens versus the l3C chemical shift of the attached carbon. [From Proton-Carbon Chemical Shift Correlations, by R. S. Macomber, Journal of Chemical Education, 68, 284-285 (1991). Reprinted with permission.]...

A critical analysis of the neutron data [245] suggested that well-designed experiments on single crystals suited for high precision in both fields could yield a very valuable correlation between proton chemical shifts and hydrogen-bond lengths. 

Reuben J (1986) Intramolecular hydrogen bonding as reflected in the deuterium isotope effects on carbon-13 chemical shifts. Correlation with hydrogen bond energies. J Am Chem Soc 108 1735-1738... 

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