Structural and dynamical study of acetaldoxime by means of 14N nuclear quadrupole resonance

The temperature dependence of 14N NQR frequency, 14N spin—lattice relaxation time, DTA and the second moment of 1H NMR was observed for acetaldoxime. The occurrence of a minimum relaxation time near 150 K is attributed to the reorientation of the methyl group. The activation energy for this motion was found to be 9.8 kJ mol−1. Above 210 K, the relaxation is dominated by two different motions. The activation energies for these motions were found to be 10.4 and 59.6 kJ mol−1. The latter energy is considered to correspond to the reorientation of the OH group about the C  N bond. The phase transition observed at about 250 K and the fade-out phenomenon of the NQR lines near 250 K are attributable to the above motion. The Z—E isomerization could not be observed in the temperature range between 77 and 255 K.