Abstract (EN):
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 Delta (g)(cr)H(m)degrees were 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 degrees = 10(5) Pa, molar enthalpies, entropies and Gibbs energies of sublimation at T = 298.15 K, were derived: [GRAPHICS] (C) 2001 Academic Press.
Idioma:
Inglês
Tipo (Avaliação Docente):
Científica
Nº de páginas:
11