科研之友
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摘要
The fusion, vaporization, and sublimation enthalpies of a series of perfluorinated alkanes have been measured by combining measurements obtained by differential scanning calorimetry (DSC), transpiration, and correlation-gas chromatography and comparing the results to available data in the literature. Additionally, experiments are reported to provide a guide in identifying appropriate structural features of fluorinated compounds suitable for use as standards in correlation gas chromatography measurements. Fusion enthalpies and fusion temperatures by DSC for the following compounds were measured (in kJ.mol(-1); K): decafluorobiphenyl (20.5 +/- 0.6, 339.6), perfluorododecane (24.2 +/- 0.6, 346.6), perfluorotridecane (27.9 +/- 0.4, 361.7), perfluorotetradecane (31.5 +/- 0.3, 375.6), perfluoropentadecane (35.1 +/- 0.2, 388.1), perfluorohexadecane (38.7 +/- 0.1, 399.7), perfluoroeicosane (50.3 +/- 0.3, 436.2), and perfluorotetracosane (63.2 +/- 0.6, 461.1). Sublimation enthalpies for the following compounds were measured by transpiration (in kJ.mol(-1); T = 298.15 K): perfluorododecane (85.8 +/- 0.6), perfluorotridecane (94.3 +/- 0.5), perfluorotetradecane (102.4 +/- 1.0), and perfluoropentadecane (109.4 +/- 0.4). Vaporization and sublimation enthalpies, respectively, were also evaluated for the following compounds (kJ.mol(-1); T/K = 298.15): perfluorohexadecane (88.6 +/- 4.0, 117.6 +/- 4.9), perfluoroeicosane (113.7 +/- 7.4, 148 +/- 8.8), and perfluorotetracosane (141.4 +/- 2.2, 168.3 +/- 11.1). The measured vaporization enthalpies of the perfluorinated alkanes behave linearly as a function of the number of CF2 groups similar to what is observed with n-alkanes. Correlation-gas chromatography experiments confirmed previous findings that hydrocarbons can be used as standards for compounds containing a few fluorine atoms but otherwise standards need to be chosen with similar fluorine substitution and functionality.
- 出版日期2012-8
