NMR-STUDY OF POLYCRYSTALLINE AZOLES

Polycrystalline pyrazole, imidazole and benzotriazole were investigated by H-1 and H-2 NMR spectroscopy. In addition to the usual broad line of the H-1 NMR signal due to the dipole-dipole interaction, a significantly narrowed component (DELTA-nu = 1-2 kHz) of a complex triplet structure was detected in all three compounds. To interpret this observation, a mechanism with virtually complete averaging of the dipole-dipole interaction for a small part of the sample protons is suggested. The mechanism is based on proton interaction with the unpaired electron of a short-lived radical of the type Az. or (H-Az.-H).