Thermodynamic properties of fluorine compounds. Part 11.—Low-temperature heat capacities of the three tetrafluorobenzenes
- 1 January 1973
- journal article
- research article
- Published by Royal Society of Chemistry (RSC) in Journal of the Chemical Society, Faraday Transactions 1: Physical Chemistry in Condensed Phases
- Vol. 69, 761-770
- https://doi.org/10.1039/f19736900761
Abstract
The heat capacities of 1,2,3,4-, 1,2,3,5- and 1,2,4,5-tetrafluorobenzene were measured by adiabatic calorimetry at temperatures between 11 and 353 K. Enthalpies of phase transitions were also measured. The entropies of the liquids at 298.15 K were calculated from the measurements as 256.1, 257.3 and 250.4 J K–1 mol–1 respectively. The heat capacity curve for 1,2,3,5-tetrafluorobenzene showed that a transition occurred in the crystals just below the melting temperature. 1,2,3,4-tetrafluorobenzene crystallised first in a metastable form which, on cooling, rapidly transformed to stable crystals. No anomalies were found in the heat capacity curve of 1,2,4,5-tetrafluorobenzene.Keywords
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