SPECTROSCOPIC INVESTIGATIONS OF PHASE TRANSITION IN 5-CHLORO-2-PYRIDONE

Article abstract of DOI:10.1016/0022-2860(87)87044-8

Spectroscopic investigation of 5-chloro-2-pyridone has been carried out in the temperature range 77-300 K.At room temperature the ³⁵Cl NQR spectrum shows a single line at 35.618 MHz, but at 250.7 K two lines appear at 35.850 MHZ and 35.840 MHz respectively indicating the presence of a phase transition.IR, far-IR, laser Raman and dielectric measurements have been carried out to investigate the phase transition further.Low temperature IR studies show splitting of ν(C-Cl), β(N-H) and ν(C=O) bands at T_c.Dielectric measurements show a small, but finite, change in the value of the dielectric constant around T_c.Raman spectra at different temperatures support the existence of a new phase, as shown by the appearance of a new band at 81 cm^-1, the frequency of which changes slowly as T_c is approached and which disappears at T_c.The temperature dependence of the NQR frequencies has been analysed using Bayer Kushida and Brown equations to evaluate the torsional frequencies.