Phase Transitions in the Quinol Clathrate Compounds. I. The Quinol Hydrogen Cyanide Clathrate Compound

The heat capacity of the clathrate compound of quinol with hydrogen cyanide was measured from 12 to 300 K. It exhibited a well defined anomaly at 177.8+0.1 K. The entropy change associated with it was estimated to be 5.71±0.3 J/mol K. This value is close to Rln2, implying that the anomalous heat capacity is due to the order-disorder phase transition concerned with the orientation of the trapped molecules. Dielectric study supported this view. Far infrared spectra of the crystal was recorded from 38 to 500 cm -1 over a range of temperature. Two bands at 46 and 95 cm -1 were found to be characteristic of this substance. A possible assignment of the former band was proposed. Finally, the lattice sum calculation showed that the dipole interaction energy between the guest molecules corresponds to 318 K of temperature compared with the observed transition temperature.