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Manuel A.V. Ribeiro da Silva Luísa M.P.F. Amaral Cristina R.P. Boaventura Jos R.B. Gomes 《The Journal of chemical thermodynamics》2008,40(8):1226-1231
The standard (p = 0.1 MPa) molar enthalpies of formation of 2-, 3- and 4-cyanobenzoic acids were derived from their standard molar energies of combustion, in oxygen, at T = 298.15 K, measured by static bomb combustion calorimetry. The Calvet high temperature vacuum sublimation technique was used to measure the enthalpies of sublimation of 2- and 3-cyanobenzoic acids. The standard molar enthalpies of formation of the three compounds, in the gaseous phase, at T = 298.15 K, have been derived from the corresponding standard molar enthalpies of formation in the condensed phase and standard molar enthalpies for phase transition. The results obtained are −(150.7 ± 2.0) kJ · mol−1, −(153.6 ± 1.7) kJ · mol−1 and −(157.1 ± 1.4) kJ · mol−1 for 2-cyano, 3-cyano and 4-cyanobenzoic acids, respectively. Standard molar enthalpies of formation were also estimated by employing two different methodologies: one based on the Cox scheme and the other one based on several different computational approaches. The calculated values show a good agreement with the experimental values obtained in this work. 相似文献
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The standard (p0 = 0.1 MPa) molar enthalpies of formation of several crystalline lithium alkoxides, ΔHf0(LiOR, cr), have been determined by reaction-solution calorimetry at 298.15 K. A linear correlation has been found between ΔHf0(LiOR, cr) and ΔHf0(ROH, 1) for R = n-alkyl, enabling the prediction of data for other lithium alkoxides. The deviations from the linear correlation observed for R =iPr and tBu were tentatively explained in terms of the electronegativities of the OR groups. The experimental data were also used to derive the lattice energies and the thermochemical radii of the anions OR−. The results were compared with those derived from the enthalpies of formation of the analogous sodium alkoxides, reported in a previous publication. 相似文献
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Manuel A.V. Ribeiro da Silva Luísa M.P.F. Amaral 《The Journal of chemical thermodynamics》2009,41(3):349-354
The standard (p° = 0.1 MPa) molar enthalpies of combustion, , for crystalline 2-furanacrylic acid, 3-furanacrylic acid, and 3-(2-furyl)-2-propenal and for the liquid 2-furanacrylonitrile were determined, at the temperature 298.15 K, using a static bomb combustion calorimeter. For these compounds, the standard molar enthalpies of phase transition, , at T = 298.15 K, were determined by Calvet microcalorimetry. For the two crystalline furanacrylic acids the vapour pressures as function of temperature were measured by the Knudsen effusion technique and the standard molar enthalpies of sublimation, , at T = 298.15 K were derived by the Clausius–Clapeyron equation. The results are as follows:
Empty Cell | |||
Calvet | Knudsen | ||
2-Furanacrylic acid (cr) | 3149.8 ± 0.5 | 103.0 ± 0.7 | 103.3 ± 0.5 |
3-Furanacrylic acid (cr) | 3151.5 ± 0.7 | 104.9 ± 1.1 | 106.8 ± 0.5 |
3-(2-Furyl)-2-propenal (cr) | 3425.7 ± 1.2 | 82.3 ± 0.4 | |
2-Furanacrylonitrile (l) | 3562.5 ± 1.3 | 65.2 ± 0.6 |