An Examination of the Thermodynamics of Fusion, Vaporization, and Sublimation of (R,S)-and (R)-Flurbiprofen by Correlation Gas Chromatography

ABSTRACT: The vaporization, fusion, and sublimation enthalpies of (R,S)-and (R)-flurbiprofen at T = 298.15 K are reported and compared with literature values when available. Correlation gas chromatography experiments were first performed to identify appropriate standards that could be used for materials containing a single fluorine substituent. Subsequent correlations resulted in a vaporization enthalpy for (R,S)-flurbiprofen and (R)-flurbiprofen, H vap (298.15 K), of (127.5 ± 5.5) and (127.4 ± 4.7) kJ mol, respectively. Fusion enthalpies, H fus (387 K), of (28.2 ± and, H fus (381 K), (22.8 ± kJ mol −1 were also measured by differential scanning calorimetry for the racemic and chiral forms of flurbiprofen. Adjusted to T = 298.15 K and combined with the vaporization enthalpy resulted in sublimation enthalpies, H sub (298.15 K), of (155.6 ± 5.8) and (145.1 ± 5.7) kJ mol −1 for (R,S)-and (R)-flurbiprofen, respectively. The fusion enthalpy measured for the racemic form was in excellent agreement with the literature value, while the sublimation enthalpy varies substantially from previous work. Two weak solid-solid phase transitions were also observed for (R)-flurbiprofen at T = 353.9 K (0.30 ± 0.1) and 363.2 K (0.21 ± 0.03) kJ·mol −1