NMR Spectroscopic Properties of Sulphur

The most important NMR properties12 of 33S, which is the only isotope of sulphur with a non-zero spin, are shown in Table 1. 

Besides electronic symmetry, other factors that can affect NMR line widths, such as chemical exchange, viscosity and temperature, can often preclude the detection of 33S NMR signals. 

Large line widths (i) prevent the accurate measurement of chemical shifts, (ii) may cause the overlap of resonances when more than one type of sulphur atom is present in a molecule or sample and (iii) have a significant influence on the achievable signal-to-noise ratio (S/N) and, consequently, on the experimental times needed to obtain readable spectra. 

1 Natural abundance Magnetogyric ratio y/107 rad s 1T 1 Magnetic moment J./ J,N Quadrupole moment Q/barn Receptivity3 Cf Dc 

Moreover, the low magnetogyric ratio results in very low resonance frequencies and accentuates the effects of spurious signals in the first part of the FID. These signals cause severe baseline distortions in the FT spectrum, thus preventing a precise measurement of spectral parameters (chemical shift, line width and signal amplitude), especially in the case of broad resonances. 

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