Enthalpies and entropies of sublimation, vaporization and fusion of nine polyhydric alcohols

Abstract

The thermodynamics of phase transitions of nine polyhydric alcohols have been studied by different experimental approaches. The enthalpy and entropy changes associated with sublimation of pentaerythritol and myo-inositol, and the vaporization of meso-erythritol, adonitol, D-arabinitol, xylitol, dulcitol, D-mannitol, D-sorbitol and myo-inositol were determined from the temperature dependence of their vapour pressures, as measured by the torsion–effusion method. The enthalpies and temperatures of fusion were measured by differential scanning calorimetry and relevant entropies were also obtained.

Enthalpies and entropies of sublimation at 298 K have been derived from the experimental data by considering the appropriate C_p values partly estimated through the group additivity schemes. Results are fairly constant for each class of polyols and in particular Δ_subX⁰₂₉₈(tetritols)≈Δ_subX⁰₂₉₈(pentitols) < Δ_subX⁰₂₉₈(hexitols), but D-sorbitol and myo-inositol show lower values. Sublimation is discussed on the basis of the crystal structure data in the literature.