Thermodynamic study on the sublimation of 3-phenylpropionic acid and of three methoxy-substituted 3-phenylpropionic acids

• Published in: The Journal of chemical thermodynamics 2001-08, Vol.33 (8), p.837-847
• Main Authors: Monte, Manuel J.S., Hillesheim, Dorothea M.
• Format: Article
• Language: English
• Subjects: Chemical thermodynamics; Chemistry; Elements, mineral and organic compounds; enthalpies of sublimation; entropies of sublimation; Exact sciences and technology; General and physical chemistry; phenylpropionic acids; standard Gibbs energies of sublimation; Thermodynamic properties; vapour pressures
• ISSN: 0021-9614; 1096-3626
• DOI: 10.1006/jcht.2000.0767

The Knudsen mass-loss effusion technique was used to measure the vapour pressures at different temperatures of the following compounds: 3-phenylpropionic acid, between T= 305.17 K and T= 315.17 K; 3-(2-methoxyphenyl)propionic acid, between T= 331.16 K and T= 347.16 K; 3-(4-methoxyphenyl)propionic acid, between T= 341.19 K and T= 357.15 K; 3-(3,4-dimethoxyphenyl)propionic acid, between T= 352.18 K and T= 366.16 K. From the temperature dependence of the vapour pressure, the standard molar enthalpies of sublimation ΔcrgHmowere derived by the Clausius–Clapeyron equation and the molar entropies of sublimation at equilibrium pressures were calculated. On the basis of estimated values for the heat capacity differences between the gas and the crystal phases of the studied compounds the standard, p∘= 105Pa, molar enthalpies, entropies and Gibbs energies of sublimation at T= 298.15 K, were derived: