(23Na) Sodium NMR

Safety note: Some of the materials mentioned here are very dangerous. Ask a qualified chemist for advice before handling them. Qualified chemists should check the relevant safety literature before handling or giving advice about unfamiliar substances. NMR solvents are toxic and most are flammable. Specifically, sodium salts are non-toxic on account of their sodium under normal circumstances, however, their anions may be toxic.

23Sodium NMR

23Sodium (23Na) is a medium sensitivity nucleus that yields slightly broad lines over a moderate chemical shift range. 23Na is a spin 3/2 nucleus and is therefore quadrupolar. As a result, the signal width increases with asymmetry of the environment. Hence, in the spectra in fig. 1, NaCl is narrower than NaOH that is narrower than a PAH salt (disodium 9,10-diphylanthracenediide). The main use of sodium NMR is to determine the presence of sodium or the number of different chemical sites that it occupies. There is little information available about chemical shifts (fig. 2).

Fig. 1. 23Na-NMR spectra of NaOH, NaCl and an organometallic sodium salt showing the variation in line-width

Sodium spectra

Fig. 2. Chemical shift ranges for 23Na NMR

Chemical shifts of sodium

Properties of 23Na

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Natural abundance100%
Chemical shift range72 ppm, from -62 to 10
Frequency ratio (Ξ)26.451900%
Reference compound0.1 M NaCl in D2O
Linewidth of reference8.2 Hz
T1 of reference0.1 s
Receptivity rel. to 1H at natural abundance0.0927
Receptivity rel. to 1H when enriched0.0927
Receptivity rel. to 13C at natural abundance545
Receptivity rel. to 13C when enriched545
Linewidth parameter140 fm4

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