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, carbon disulfide is a toxic carcinogen: wear protective gloves and work in a hood.

³³Sulfur NMR

³³Sulfur (³³S)is a low sensitivity nucleus with a low natural abundance that yields very broad lines over a wide chemical shift range. ³³S is a spin 3/2 nucleus and is therefore quadrupolar. As a result, the signal width increases with asymmetry of the environment. Hence, inorganic sulfates and sulfites yield moderately broad signals and small organic sulfites and sulfates are observable. Only the smallest organic sulfides such as CS₂ (fig. 1) yield observable signals with a high-resolution spectrometer with DMSO being just too broad (10's of kHz) to be observed. Because of its low sensitivity and broad signals, ³³S NMR is little used in high resolution NMR and when it is used it is mostly for sulfates and sulfites. Each type of sulfur signal has its characteristic chemical shifts (fig. 2).

Fig. 1. ³³S-NMR spectra of saturated (NH₄)₂SO₄ in D₂O and neat CS₂ showing increasing linewidth with increasing environmental asymmetry

Fig. 2. Chemical shift ranges for sulfur NMR

Properties of ³³S

(Click here for explanation)

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