Low-temperature calorimetric studies ofcis- andtrans-perfluorobicyclo(4,3,0)nonanes

✍ Scribed by R.M. Varushchenko; A.I. Druzhinina

• Publisher: Elsevier Science
• Year: 1998
• Tongue: English
• Weight: 177 KB
• Volume: 30
• Category: Article
• ISSN: 0021-9614
• DOI: 10.1006/jcht.1997.0336

✦ Synopsis

The heat capacities of the crystalline, plastic crystalline, and liquid phases of trans-and Ž . cis-perfluorobicyclo 4,3,0 nonanes were measured by vacuum adiabatic calorimetry over the temperature range 5 K to 350 K and 5 K to 354 K, respectively. Two solid-to-solid phase Ž . Ž . transitions for the cis-isomer at T III to II s 200.64 K and T II to I s 245.63 K and trs trs Ž . one transition for the trans-isomer at T II to I s 236.63 K were found. The triple point trs temperatures of the compounds are T s 291.27 K and T s 248.05 K, respectively. The tp

enthalpies and entropies of transition and fusion and the main thermodynamic functions have been obtained. A conclusion was drawn, on the basis of large values of solid-to-solid transition entropies and small values of fusion entropies, that both substances form plastic crystals. The thermodynamic properties of some bicyclic perfluorocarbons were compared with corresponding values for their hydrogen-containing analogs.