# Spectroscopic investigations of phase transition in 5-chloro-2-pyridone

Raghoottama, PS and Soundararajan, S and Ramakrishna, J (1987) Spectroscopic investigations of phase transition in 5-chloro-2-pyridone. In: Journal of Molecular Structure, 157 (4). pp. 371-384.

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## Abstract

Spectroscopic investigation of 5-chloro-2-pyridone has been carried out in the temperature range 77–300 K. At room temperature the $^{35}Cl NQR$ 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 \nu(C---Cl), \beta(N---H) and \nu(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 toevaluate the torsional frequencies.

Item Type: Journal Article Copyright belongs to Elsevier Science Division of Physical & Mathematical Sciences > PhysicsDivision of Chemical Sciences > Inorganic & Physical Chemistry 19 Mar 2008 19 Sep 2010 04:43 http://eprints.iisc.ernet.in/id/eprint/13230