The enthalpies of vaporization and sublimation of exo- and endo-tetrahydrodicyclopentadienes at T=298.15K
| Autor: | Dorothea M. Hillesheim, James S. Chickos, Gary Nichols, Michael J. Zehe |
|---|---|
| Rok vydání: | 2002 |
| Předmět: |
Chemistry
Stereochemistry Enthalpy Enthalpy of vaporization Atomic and Molecular Physics and Optics Standard enthalpy of formation Differential scanning calorimetry Enthalpy of sublimation Vaporization Physical chemistry General Materials Science Sublimation (phase transition) Plastic crystal Physical and Theoretical Chemistry |
| Zdroj: | The Journal of Chemical Thermodynamics. 34:1647-1658 |
| ISSN: | 0021-9614 |
| DOI: | 10.1016/s0021-9614(02)00229-x |
| Popis: | The vaporization enthalpies {ΔglHm (298.15 K)} of endo- and exo-tetrahydrodicyclopentadiene (THDCPD) have been measured by correlation gas chromatography. Values of (50.2±2.3) kJ · mol −1 and (49.1±2.3) kJ · mol −1 have been obtained for the endo and exo isomers, respectively. The sublimation enthalpy of the endo isomer { Δ g cr H m (298.15 K )=(51.2±2.4) kJ · mol −1 } has been obtained by combining fusion and vaporization enthalpies adjusted as necessary to T=298.15 K. Low-temperature d.s.c. studies of both isomers reveal solid-to-solid phase transitions. The endo isomer, which is a plastic crystal at room temperature, exhibits a solid-to-solid phase transition at T=214 K { Δ cr (1) cr (2) H m (214 K )=(10.7±0.13) kJ · mol −1 } and a melting temperature of 356.8 K { Δ l cr (1) H m (356.8 K )=(3.48±0.2) kJ · mol −1 } with some evidence of polymorphism. The exo isomer exhibits a solid phase transition at T=162.1 K { Δ cr (1) cr (2) H m (162.1 K )=(3.18±0.11) kJ · mol −1 } and a melting temperature of 183.2 K { Δ l cr (1) H m (183.2 K )=(1.20±0.04) kJ · mol −1 } . Enthalpies of vaporization and sublimation are combined with the respective enthalpies of formation previously reported to yield the following gas-phase values: for endo THDCPD, Δ f H ∘ m =−(61.9±3.2) kJ · mol −1 ; and for exo-THDCPD, Δ f H ∘ m =−(73.7±2.7) kJ · mol −1 . |
| Databáze: | OpenAIRE |
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