Crystalline and liquid vapour pressures of the four p-monohalophenols: A thermodynamic study of their phase transitions

Abstract

Vapour pressures of condensed phases of p-monohalophenols were measured over the temperature ranges (265.6 to 342.8)K, (273.5 to 331.0)K, (285.3 to 370.5)K and (307.2 to 380.4)K, respectively for p-fluoro, p-chloro, p-bromo and p-iodophenol, using a static method based on diaphragm capacitance gauges. The results obtained for each compound, enabled the determination of the standard molar enthalpies, Gibbs energies and entropies of sublimation and of vaporisation, at T=298.15K as well as phase diagram representations of the (p,T) experimental results. The temperatures and molar enthalpies of fusion were determined using DSC and were compared with the values derived from the vapour pressure measurements. Correlations involving thermodynamic properties and also the volume of the halogen substituent of p-halophenols are presented and compared to the ones derived before for related methyl p-halobenzoates and p-halobenzoic acids. Vapour pressures, at T=298.15K, of the compounds included in the three families are well described by a single correlation based on the temperature of fusion and on the volume of the halogen atom.