Authors:X. Zielenkiewicz, G. Perlovich, and M. Wszelaka-Rylik
A new device, based on the inert gas flow method, for measuring the vapour pressure and the determination of the enthalpy of sublimation in a wide range of temperatures (up to 573 K) is described in this paper. The limits of the flow rate as important experimental parameter were determined for the given instrument. The results of calibration showed a good precision and reproducibility of the measurements of the enthalpy of sublimation. The results of the determination of some derivatives of pyrimidine were presented.
Authors:P. Storoniak, K. Krzymiński, and J. Błażejowski
Enthalpies of sublimation of acridine, 9-acridinamine, N-methyl-9-acridinamine, 10-methyl-9-acridinimine, N,N-dimethyl-9-acridinamine
and N-methyl-10-methyl-9-acridinimine were determined by fitting to thermogravimetric curves with the Clausius-Clapeyron relationship.
These values compare well with crystal lattice energies predicted theoretically as the sum of electrostatic, dispersive and
repulsive interactions. Partial charges for these calculations were obtained on an ab initio level, while atomic parameters
were taken from literature.
Correlations between the enthalpyofsublimation and the temperature of sublimation at a reference pressure, or between the enthalpyofsublimation and the standard Gibbs energy of sublimation at 298.15 K have been
Enthalpies and entropies of sublimation for N-acetylglycine amide (NAGA), N-acetyl-L-alanine amide (L-NAAA), and N-acetyl-D-leucine amide (D-NALA) were determined from the dependence of their vapour pressures on temperature, as measured by the torsion-effusion method.
The present work reports the experimental determination of the standard (po = 0.1 MPa) molar enthalpies of formation in the condensed and gaseous phases, at T = 298.15 K, of 5- and 6-nitroindazole. These results were derived from the measurements of the standard molar energies of
combustion, using a static bomb calorimeter and from the standard molar enthalpies of sublimation derived by the application
of Clausius–Clapeyron to the temperature dependence of the vapour pressures measured by the Knudsen effusion technique. The
results are interpreted in terms of the energetic contributions of the nitro groups in the different positions of the aromatic
at T = 298.15 K, of 2-acetyl-5-nitrothiophene and 5-nitro-2-thiophenecarboxaldehyde as −(48.8 ± 1.6) and (4.4 ± 1.3) kJ mol−1, respectively. These values were derived from experimental thermodynamic parameters, namely, the standard (po = 0.1 MPa) molar enthalpies of formation, in the crystalline phase,
measured by rotating bomb combustion calorimetry, and from the standard molar enthalpies of sublimation, at T = 298.15 K, determined from the temperature–vapour pressure dependence, obtained by the Knudsen mass loss effusion method.
The results are interpreted in terms of enthalpic increments and the enthalpic contribution of the nitro group in the substituted
thiophene ring is compared with the same contribution in other structurally similar compounds.
, respectively, were derived from the standard molar energies of combustion, in oxygen, to yield CO2(g) and H2O(l), at T = 298.15 K, measured by static bomb combustion calorimetry. The Knudsen mass-loss effusion technique was used to measure
the dependence of the vapour pressure of the solid isomers of hydroxymethylphenol with the temperature, from which the standard
molar enthalpies of sublimation were derived using the Clausius–Clapeyron equation. The results were as follows:
, for 2-, 3- and 4-hydroxymethylphenol, respectively. From these values, the standard molar enthalpies of formation of the
title compounds in their gaseous phases, at T = 298.15 K, were derived and interpreted in terms of molecular structure. Moreover, using estimated values for the heat capacity
differences between the gas and the crystal phases, the standard (p° = 0.1 MPa) molar enthalpies, entropies and Gibbs energies of sublimation, at T = 298.15 K, were derived for the three hydroxymethylphenols.
Authors:Luis H. Blanco, Yina P. Salamanca, and Edgar F. Vargas
between the enthalpy of solution at infinite dilution, , and the enthalpyofsublimation, , according to the equation:
where α is the thermal expansion of the solvent. The last term in Eq. 1 accounts for the correction of the experimental
Authors:Yu. Maksimuk, V. Sokolov, V. Sevruk, and P. Trahanov
The enthalpies of combustion for 4-formylbenzoic acid (I), 4-methylbenzyl alcohol (II), and trimethyl 1,2,4-benzenetricarboxylate
(III) were determined by the bomb calorimetry method. Enthalpies of sublimation for I and II were measured with a calorimeter.
The contributions of different substituents to the standard enthalpies of formation for benzene derivatives in the gas state