共查询到20条相似文献,搜索用时 46 毫秒
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Clara C.S. Sousa M. Agostinha R. Matos Victor M.F. Morais 《The Journal of chemical thermodynamics》2011,43(8):1159-1163
In this work, we have determined the experimental standard molar enthalpies of formation, in the gas phase, of 2,6-dimethyl-4-pyrone ?(261.5 ± 2.6) kJ · mol?1 and 2-ethyl-3-hydroxy-4-pyrone ?(420.9 ± 2.8) kJ · mol?1. These values were obtained by combining the standard molar enthalpy of formation in the condensed phase, derived from combustion experiments in oxygen, at T = 298.15 K, in a static bomb calorimeter, with the standard molar enthalpy of sublimation, at T = 298.15 K, obtained by Calvet microcalorimetry. Additionally, high-level density functional theory calculations using the B3LYP hybrid exchange-correlation energy functional with extended basis sets have been performed for these two compounds. Good agreement was obtained between the experimental and computational results. Using the same methodology, we calculated the standard molar enthalpy of formation of gaseous 2-methyl-3-hydroxy-4-pyrone. 相似文献
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Vera L.S. Freitas José R.B. Gomes Maria D.M.C. Ribeiro da Silva 《The Journal of chemical thermodynamics》2010,42(2):251-255
The standard () molar enthalpy of formation of 4-methyldibenzothiophene, in the gaseous phase, at T = 298.15 K, was derived from the combination of the values of the standard molar enthalpy of formation, in the crystalline phase, at T = 298.15 K, and the standard molar enthalpy of sublimation, at the same temperature. The standard molar enthalpy of formation in the crystalline phase, determined from the standard massic energy of combustion, in oxygen, is (70.9 ± 4.8) kJ · mol?1 and was measured by rotating-bomb combustion calorimetry. From Calvet microcalorimetry measurements, the standard molar enthalpy of sublimation obtained is (90.3 ± 0.7) kJ · mol?1. 相似文献
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Ana Filipa L.O.M. Santos André R. Monteiro Jorge M. Gonçalves William E. Acree Maria D.M.C. Ribeiro da Silva 《The Journal of chemical thermodynamics》2011,43(7):1044-1049
In this paper, the first, second and mean (N?O) bond dissociation enthalpies (BDEs) were derived from the standard (p° = 0.1 MPa) molar enthalpies of formation, in the gaseous phase, , at T = 298.15 K, of 2,2′-dipyridil N-oxide and 2,2′-dipyridil N,N′-dioxide. These values were calculated from experimental thermodynamic parameters, namely from the standard (p° = 0.1 MPa) molar enthalpies of formation, in the crystalline phase, , at T = 298.15 K, obtained from the standard molar enthalpies of combustion, , measured by static bomb combustion calorimetry, and from the standard molar enthalpies of sublimation, at T = 298.15 K, determined from Knudsen mass-loss effusion method. 相似文献
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The density, relative permittivity, viscosity and speed of sound at T = (293.15, 298.15, 303.15, 308.15, and 313.15) K in the binary mixtures of nitromethane with 2-methoxyethanol and 2-butoxyethanol have been measured as a function of composition. From the experimental results, the excess molar volumes VE, excess Gibbs free energy of activation for viscous flow , excess isentropic compressibility and the deviations in the relative permittivity, viscosity, and speed of sound from a mole fraction average have been calculated. The viscosity data, at T = 298.15 K, were correlated with equations of Hind et al., Grunberg and Nissan, Frenkel, and McAllister. The results are discussed in terms of intermolecular interactions and structure of studied binary mixtures. 相似文献
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Manuel A.V. Ribeiro da Silva Luís M.N.B.F. Santos Luís M. Spencer S. Lima 《The Journal of chemical thermodynamics》2010,42(1):134-139
The energetic study of 1,2,3-triphenylbenzene (1,2,3-TPhB) and 1,3,5-triphenylbenzene (1,3,5-TPhB) isomers was carried out by making use of the mini-bomb combustion calorimetry and Knudsen mass-loss effusion techniques. The mini-bomb combustion calorimetry technique was used to derive the standard (p° = 0.1 MPa) molar enthalpies of formation in the crystalline state from the measured standard molar energies of combustion for both isomers. The Knudsen mass-loss effusion technique was used to measure the dependence with the temperature of the vapour pressure of crystalline 1,2,3-TPhB, which allowed the derivation of the standard molar enthalpy of sublimation, by application of the Clausius–Clapeyron equation. The sublimation study of 1,3,5-TPhB had been performed previously. From the combination of data obtained by both techniques, the standard molar enthalpies of formation in the gaseous state, for both isomers, at T = 298.15 K, were calculated. The results indicate a higher stability of the 1,3,5-TPhB isomer relative to 1,2,3-TPhB, similarly to the terphenyls. Nevertheless, the 1,2,3-TPhB isomer is not as energetically destabilized as one might expect, supporting the existence of a π–π displacive stacking interaction between both pairs of outer phenyl rings. The volatility difference between the two isomers is ruled by the enthalpy of sublimation. The volatility of the 1,2,3-TPhB is two orders of magnitude higher than the 1,3,5-TPhB isomer, at T = 298.15 K.
Empty Cell | |||
1,2,3-Triphenylbenzene (1,2,3-TPhB) | ?12248.2 ± 4.1 | 376.7 ± 5.3 | |
1,3,5-Triphenylbenzene (1,3,5-TPhB) | ?12224.6 ± 3.6 | 366.8 ± 4.9 |
Empty Cell | |||
1-Ethylpiperidine | 4776.8 ± 1.6 | 39.44 ± 0.65 | |
2-Ethylpiperidine | 4740.3 ± 1.5 | 48.22 ± 0.89 |
Empty Cell | /(kJ · mol?1) | /(kJ · mol?1) | /(kJ · mol?1) |
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2-Chloronitrobenzene | 2939.5 ± 0.7 | 18.7 ± 1.0 | 80.9 ± 1.5 |
3-Chloronitrobenzene | 2915.8 ± 0.8 | 42.4 ± 1.2 | 82.5 ± 1.5 |
4-Chloronitrobenzene | 2921.7 ± 1.4 | 36.5 ± 1.6 | 76.2 ± 2.1 |
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