The use of supercritical fluids as solvents for NMR spectroscopy

The use of supercritical fluids as solvents in high-pressure NMR spectroscopy was described. A supercritical fluid can be defined for a single component as a solvent above its critical temperature and critical pressure such that no change in pressure can introduce a phase transition in the single fluid phase. NMR relaxation measurements provide information about the rotational and spatial reorientation of molecules in liquids and supercritical fluid solutions. The results show that the high-pressure NMR investigations of homogeneous catalytic reactions in pressurized liquids are useful in identifying reaction intermediates and the resting states of the catalyst.