NMR Spectroscopy of Nuclei Other Than Protons

By accident, almost all the nuclei of interest to the vast majority of chemists have spins 7=1/2 and hence do not differ at all from protons in their basic theoretical aspects. However, their usefulness does not warrant the effort of learning any empirical parameters relating to them, so the remarks below do not reflect the amount of data available. 

It must be realized that the effect of spin-spin coupling of protons to other magnetic nuclei may be observed in the proton spectra, and hence some idea of the magnitudes of coupling between protons and some commonly occurring magnetic nuclei may be useful in interpreting proton spectra. 

Fluorine resonates over a range of some 300 ppm, i.e., its chemical shift is more sensitive than H to the changes of environment. In saturated systems, /h-f for H-C-F (geminal) ranges from 40-80 Hz and for H-C-C-F (vicinal) from 0-30 Hz. The latter has a Karplus-like dependence on stereochemistry (Eqn. 12.11). 

Phosphorus resonates over about 400 ppm. /p n (direct), as in phosphine derivatives, is in the range of 200-700 Hz, i.e., of an entirely diiferent order of magnitude from interproton coupling constants. The Jh-p coupling constants for H-C-P, H-C-C-P, and H-C-O-P (as in phosphate esters) vary between 0 and 30 Hz. In phosphate esters it is generally in the range of 5 to 20 Hz and shows a Karplus-like stereochemical dependence. 

The natural abundance of is only 17o and thus spectra are difficult to observe in unenriched samples. A further disadvantage is that is a less good magnet than a proton. The overall loss of sensitivity compared to H is approximately 6000-fold. However, because of the central importance of carbon in organic chemistry, constant efforts to obtain NMR data have been made over the last 15 years. Recently (1970-1971) Fourier Transform NMR spectroscopy (see Sec. 

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Axenrod, T., Structural effects on the one-bond 15N-H coupling constant, in NMR Spectroscopy of Nuclei Other Than Protons, Axenrod, T. and Webb, G.A., Eds., Wiley Interscience, New York, 1974. 

Mann BE (1974) NMR spectroscopy of organo-transition metal complexes. In Axenrod T and Webb GA (eds.) NMR spectroscopy of Nuclei other than protons, ch. 11 153-156. New York Wiley-Interscience. 

Axenrod, T. NMR Spectroscopy of nuclei other than proton. In Axenrod, T.,... 

Wasylischen, R. NMR Spectroscopy of nuclei other than proton. Axenrod, T., Webb, G.A., (eds,) p. 105, New York Wiley Interscience 1974... 

This work was done while Roberts was at MIT. He later moved to the California Institute of Technology, where he became a leader in applying NMR spectroscopy to nuclei other than protons, especially Cand N. 

G. C, Levy and J. D. Cargioli, Si Fourier Transform NMR, in "Nuclear Magnetic Resonance Spectroscopy of Nuclei Other than Protons", T. Axenrod and G. A. Webb (eds.), Wiley, New York, 1974, p. 251. 

Maciel, G. E., Pulse Fourier Transform NMR with Metal Nuclei, in Axenrod, T., Webb, G. A., Nuclear Magnetic Resonance Spectroscopy of Nuclei Other than Protons, Wiley, New York 1974, pp. 347/75. 

Nuclear resonance spectroscopy is based on the nuclear resonance effect, which can occur only in nuclei containing odd numbers of protons and/or neutrons in so far as such nuclei have intrinsic magnetic moments. In other words, NMR is theoretically applicable for nuclei with the nuclear spin number I larger than 0 however, practically only nuclei with 1 = 1/2 are those most used for NMR study since those with I > 1/2 possess electric quadrupole moments which broaden the line width and reduce the resolution of the spectra. 

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