Natural J coupling

Zaccari DG, Snyder JP, Peralta JE, Taurian OE, Contreras RH, Barone V (2002) Natural J Coupling (NJC) analysis of the electron Itme pair effect on NMR couplings. Part 2. The anomeric effects on IJ (C, H) couplings and its dependence tm solvent Mol Phys 100 705—715... 

The variety of 2D NMR experiments, each with its own acronym, can easily be understood by knowing the nature of the I and S spins (e.g., XH and 13C) and the type of mixing used (e.g., coherence transfer via one-bond J coupling). Two general distinctions can be made ... 

Figures 11.9 and 11.10 compare the performance of the CCSD and CCSD(T) methods, based on either an RHF or UHF reference wave function. Compared to the RMPn plot (Figure 11.71. it is seen that the infinite nature of coupled duster causesJt4o— perform somewhat better as the reference wave function becomes increasingly j)oor. While the RMP4 energy curve follows the exact out to an elongation of 1.0A, the CCSD(T) has the same accuracy out to 1.5A. Eventually, however, the wrong...

Natural Abundance. Nature provides us with nuclides in varying amounts. (See the third column in Table 1-2.) Whereas and are 100% abundant and nearly so, is present only to the extent of 1.1%. The most useful nitrogen ( " N) and oxygen ( O) nuclides occur to the extent of much less than 1%. The NMR experiment, of course, is easier with nuclides with higher natural abundance. Because so little is present, there is a very small probability of having two atoms at adjacent positions in the same molecule (0.011 X 0.011 = 0.00012, or about I in 10,000). Thus, J couplings are not easily observed between two nuclei in spectra, although procedures to measure them have been developed. 

Arnold, W.D., Oldfield, E. The chemical nature of hydrogen bonding in proteins via NMR J-couplings, chemical shifts, and AIM theory. J. Am. Chem. Soc. 2000,122,12835M1. 

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