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1.
The standard molar enthalpies of combustion of 2-aminobenzothiazole (2AB), 2-amino-4-methyl-benzothiazole (2A4MB), and 2-amino-6-methyl-benzothiazole (2A6MB) were determined in the crystalline phase at T = 298.15 K using a rotating-bomb combustion calorimeter. The molar energies of combustion of these compounds were found to be: (−4273.6 ± 0.9), (−4896.9 ± 1.1), and (−4906.9 ± 1.2) kJ · mol−1, respectively. From these values, the corresponding standard molar enthalpies of formation in the solid phase were obtained as: (59.55 ± 1.28), (2.71 ± 1.50), and (13.53 ± 1.53) kJ · mol−1, respectively. The enthalpies of formation in the gas phase were determined using the experimental enthalpies of formation in the solid phase and predicted values of the enthalpies of sublimation. Additionally, the enthalpies of formation in the gas phase were calculated by means of the Gausian-4 theory, using several gas-phase working reactions, and were compared with those found using the predicted enthalpies of sublimation. 相似文献
2.
《The Journal of chemical thermodynamics》2002,34(1):119-127
The standard ( po = 0.1 MPa) molar enthalpies of formation ΔfHmo, at the temperature 298.15 K, for crystalline 2,3,4-, 2,4,5-, 2,4,6- and 3,4,5-trichloroaniline were derived from the molar enthalpies of combustion ΔcHmoin oxygen using rotating bomb combustion calorimetry. The reaction products were CO2(g), N2(g), and HCl · 600H2O(l). The standard molar enthalpies of sublimation ΔcrgHmoat T = 298.15 K were measured by Calvet microcalorimetry. The results are as follows: The derived standard molar enthalpies of formation of the gaseous compounds were compared with values estimated by assuming the enthalpy increment for substitution of chlorine in aniline to be the same as for substitution into benzene. 相似文献
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The values of C−H and C−I bond dissociation energies were used to calculate the enthalpies of formation (δH
f
o
of 20 cyclic and conjugated hydrocarbon radicals (R′). The values of δH
f
o
(R′) were analyzed in terms of the quantitative structure-property correlation based on the additive-group model, and the
reliability of these data was shown. Based on the correlation, several strain energies of cycles and energies of conjugation
of a lone electron with a ρ-system were calculated. The additive-group method for calculation of δH
f
o
can be extended for radicals of the naphthalyl type.
For Part 2, see Ref. 1.
Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 286–288, February, 1999. 相似文献
8.
YANG Xuwu ZHU Li CHEN Sanping GAO Shengli & SHI Qizhen Department of Chemistry Shaanxi Key Laboratory of Physico-lnorganic Chemistry Northwest University Xi''''an China 《中国科学B辑(英文版)》2005,48(Z1)
Solid complexes, RE(Et2dtc)3(phen) (RE=La, Pr, Nd, Sm-Lu), were synthesized with sodium diethyldithiocarbamate (NaEt2dtc3H2O),1,10-phenanthroline (o-phen·H2O) and hydrated lanthanide chlorides in absolute ethanol. The constant-volume combustion energies of complexes,ΔcU, were determined by a precise rotating-bomb calorimeter at 298.15 K. The standard enthalpies of combustion,ΔcHmθ, and standard enthalpies of formation,ΔfHmθ, were calculated for these complexes, respectively. The experiment results showed the "tripartite effect" of rare earth. 相似文献
9.
Solid complexes, RE(Et2dtc)3(phen) (RE=La, Pr, Nd, Sm—Lu), were synthesized with sodium diethyldithiocarbamate (NaEt2dtc3H2O), 1,10-phenanthroline (o-phen•H2O) and hydrated lanthanide chlorides in absolute ethanol. The constant-volume combustion energies of complexes, Δ C U, were determined by a precise rotating-bomb calorimeter at 298.15 K. The standard enthalpies of combustion, ΔCHm θ, and standard enthalpies of formation, ΔfHm θ, were calculated for these complexes, respectively. The experiment results showed the “tripartite effect” of rare earth.
相似文献10.
《Thermochimica Acta》1986,109(1):181-192
Combustion calorimetry of the Ti-S system has been carried out under a mixed oxygen-air atmosphere (PO2 = 4×104 Pa) at 406 °C using a Calvet-type twin calorimeter. The enthalpies of formation of solid solutions for 4H'-Ti2S3, 4H-Ti2S3 and 2H-TiS2 phases in the Ti-S system have been determined. The results are compared with the heat of combustion estimated from the literature. 相似文献
11.
Katarina Bystrm 《Journal of computational chemistry》1983,4(3):308-312
A force field has been developed, on the basis of available experimental and partial retention of diatomic differential overlap (PRDDO) data, to permit molecular mechanics calculations on azoxyalkanes. The calculated structures and enthalpies of formation are in fair agreement with experimental results. The calculated enthalpies of formation and strain energies are compared with the corresponding quantities for analogous azoalkanes. 相似文献
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The enthalpies of formation (ΔH
f
o) for 23 halosubstituted radicals were determined from the published data on bond dissociation energies. The ΔH
f
o values of the corresponding molecules necessary for the calculation of ΔH
f
o of the radicals were taken from handbooks or calculated by the additive-group method. The conjugation energies of the radicals
are calculated, and the effect of substituents at the π-system on these values was shown. Errors of determination of the ΔH
f
o values of the radicals were estimated.
For Part 1, see Ref. 1.
Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 4, pp. 643–646, April, 1998. 相似文献
14.
The enthalpies of formation (ΔH f o) for 24 hydrocarbon radicals (R?), mainly polycyclic aromatic radicals with the complex structure, were determined from the published data on bond dissociation energies. The ΔH f o values of the corresponding molecules were calculated, in the majority of cases, by the macroincrement method. Calculations by the group contribution method were performed. Some ΔH f o(R?) values were compared to those calculated by the additive-group method. Calculations were performed, and the conjugation energies of the radicals were discussed. The errors of determination of the ΔH f o(R?) values found were estimated. Due to this work, the database for ΔH f o values of hydrocarbon radicals was increased more than by 25%. 相似文献
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Kenneth B. Wiberg 《Journal of computational chemistry》1984,5(2):197-199
Group equivalents which are useful for converting energies derived from ab initio calculations into enthalpies of formation have been obtained. They allow ΔHf to be estimated from 6-31G* energies with an uncertainty on the order of ±2 kcal/mol. 相似文献
18.
By using a micro-bomb calorimeter, the standard enthalpies of combustion of C60 and C70 have been determined to be - (25 947.1±8.5) and - (29 956.1 ± 8.9) kJ/mol respectively. A g. 1. c. analysis indicated that
the amounts of residual organic solvents in the samples were very small, and their effects on the final results were negligible.
The energy of combustion ofC60 determined in this work is in agreement in the uncertainty interval with that determined by means of traditional calorimeter
using macro amount of sample. The enthalpies of formation of these two substances have been derived. The strain energies in
the molecules of C60 and C70 were estimated by a bond energy scheme and by using corannulene as the model compound, the results estimated from different
methods are very close.
Project supported by the National Natural Science Foundation of China (Grant No. 29473143) 相似文献
19.
Fattahi A Kass SR Liebman JF Matos MA Miranda MS Morais VM 《Journal of the American Chemical Society》2005,127(16):6116-6122
Radical anions of o-, m-, and p-benzoquinone were produced in a Fourier transform mass spectrometer by low energy electron attachment or collision-induced dissociation and were differentiated. Classical derivatization experiments also were carried out to authenticate the ortho and meta anions. Gas-phase techniques were used to measure the proton affinities of all three radical anions and the electron affinities of o- and m-benzoquinone. By combining these results in thermodynamic cycles, we derived heats of hydrogenation of o-, m-, and p-benzoquinone (Delta(hyd)H degrees (1o, 1m, and 1p) = 42.8 +/- 4.1, 74.8 +/- 4.1, and 38.5 +/- 3.0 kcal mol(-)(1), respectively) and their heats of formation (Delta(f)H degrees (1o, 1m, and 1p) = -23.1 +/- 4.1, 6.8 +/- 4.1, and -27.7 +/- 3.0 kcal mol(-)(1), respectively). Good accord with the literature value for the para derivative was obtained. Combustion calorimetry and heats of sublimation also were measured for benzil and 3,5-di-tert-butyl-o-benzoquinone. The former heat of formation agreed with previous determinations, while the latter result (Delta(f)H degrees (g) = -73.09 +/- 0.87 kcal mol(-)(1)) was transformed to Delta(f)H degrees (1o) = -18.9 +/- 2.2 kcal mol(-)(1) by removing the effect of the tert-butyl groups via isodesmic reactions. This led to a final value of Delta(f)H degrees (1o) = -21.0 +/- 3.1 kcal mol(-)(1). Additivity was found to work well for m-benzoquinone, but BDE1 and BDE2 for 1,2- and 1,4-dihydroxybenzene differed by a remarkably small 14.1 +/- 4.2 and 23.5 +/- 3.7 kcal mol(-)(1), respectively, indicating that o- and p-benzoquinone should be excellent radical traps. 相似文献