Enthalpies and entropies of sublimation and vaporization of aza crown ethers and cryptands measured by TGA

Abstract

AbstractIn this work, the solid–gas and liquid–gas change of phase enthalpies of three aza crown ethers and two cryptands are derived from thermogravimetric data. For each of the compounds under study, the mass loss rate, dm/dt, was measured by isothermal thermogravimetry, then Pieterse and Focke equation combined with that of Clausius–Clapeyron was applied to correlate mass loss rate with temperature and to derive the respective vaporization or sublimation enthalpies at the experimental temperature and at 298.15 K. Such enthalpies are reported with the derived entropies and Gibbs energies of change of phase for the analyzed compounds. The results show a general trend of increasing value of the thermodynamic property as the number of the nitrogen atoms increases in the molecular structure of the macrocycle.