N-14 NMR spectroscopy of tertiary amines in supercritical fluids

The linewidths of N-14 NMR resonances of tertiary amines and nitrogen-conta ining heterocycles were studied in liquefied gases and supercritical fluids . Owing to a lower rotational correlation time of the solutes in the low-vi scosity fluids, the N-14 NMR linewidths were smaller than those in benzene solutions, but to a lesser extent than theoretically achievable based on th e relative solvent viscosities, The discrepancy is attributed to the free r otor correlation time, which contributes considerably to the rotational cor relation time at high temperatures and low viscosities. The use of liquid C O2 gives better results than supercritical CO2. Copyright (C) 2000 John Wil ey & Sons, Ltd.