[en] Highlights: • Enthalpies of combustion and sublimation enthalpies have been measured. • Standard gas-phase enthalpies of formation have been derived. • Gas-phase enthalpies of formation were estimated by an empirical method. - Abstract: The standard (p^∘ = 0.1 MPa) molar enthalpies of formation of 2-chloroacetophenone and 2,4’-dichloroacetophenone, in the gaseous phase, at T = 298.15 K, were derived from the combination of the values of the standard molar enthalpies of formation in the crystalline phase, at T = 298.15 K, and the standard molar enthalpies of sublimation of each compound, at the same temperature. The standard molar enthalpies of formation, in the crystalline phase, were derived from the corresponding standard massic energies of combustion, in oxygen, at T = 298.15 K, measured by rotating-bomb combustion calorimetry. The standard molar enthalpy of sublimation of 2-chloroacetophenone was measured by Calvet microcalorimetry whereas the standard molar enthalpy of sublimation for 2,4’-dichloroacetophenone was calculated by application of the Clausius–Clapeyron equation to the vapor pressures at several temperatures measured by the Knudsen effusion technique. (table) The values of the standard molar enthalpies of formation, in the gaseous phase, at T = 298.15 K, were compared with the same parameters estimated by the empirical scheme developed by Cox. The estimation schemes were extended to others chloro-substituted acetophenones

[en] The standard (p⁰=0.1 MPa) molar enthalpies of formation of crystalline thianthrene and monothiodibenzoylmethane, HDBMS, at T=298.15 K were measured by rotating-bomb calorimetry and the standard molar enthalpies of sublimation at T=298.15 K of dibenzoylmethane (HDBMO) and monothiodibenzoylmethane (HDBMS) were measured by microcalorimetry. From the present results it could be shown that, in these molecules, the intramolecular hydrogen bond energy (O-H···O), is ca. 20 kJ · mol^-1 larger than for (S-H···O)

[en] Highlights: • Experimental and computational energetic study of alkyl 1-methylpyrrolecarboxylates; Δ_fH_m^o (g) derived from Δ_fH_m^o (l) and Δ_l^gH_m^o. • Ab initio calculations for the compounds obtained by G3(MP2)//B3LYP method. • Results interpreted in terms of structural-energetic effects. -- Abstract: Calorimetric techniques, namely static bomb calorimetry and high temperature Calvet microcalorimetry were used to derive, respectively, the standard (p^o = 0.1 MPa) molar enthalpy of formation, in the liquid phase, Δ_fH_m^o(l), and the standard molar enthalpy of vaporization, at T = 298.15 K, Δ_l^gH_m^o, of the methyl 1-methyl-2-pyrrolecarboxylate (M1M2PC). These experiments allowed the determination of its standard (p^o = 0.1 MPa) molar enthalpy of formation, in the gaseous phase, Δ_fH_m^o(g) = −(270.3 ± 2.2) kJ · mol⁻¹, at T = 298.15 K. Additionally, the standard molar enthalpy of formation of M1M2PC was estimated by computations based on standard ab initio molecular calculations at the G3(MP2)//B3LYP level. The estimated values are in very good agreement with experimental one, giving us support to estimate the gas-phase enthalpies of formation of the methyl 1-methyl-3-pyrrolecarboxylate (M1M3PC), ethyl 1-methyl-2-pyrrolecarboxylate (E1M2PC) and ethyl 1-methyl-3-pyrrolecarboxylate (E1M3PC), that were not studied experimentally. The molecular structures of the four molecules were established and the structural parameters were determined at the B3LYP/6-31G(d) level of theory. Furthermore, all the results were interpreted in terms of enthalpic increments

[en] Highlights: • Experimental and computational energetic study of alkyl 1-methylpyrrolecarboxylates. • Δ_fH_m^o (g) derived from Δ_fH_m^o (l) and Δ_l^gH_m^o. • Ab initio calculations for the compounds obtained by G3(MP2)//B3LYP method. • Results interpreted in terms of structural-energetic effects. - Abstract: Calorimetric techniques, namely static bomb calorimetry and high temperature Calvet microcalorimetry were used to derive, respectively, the standard (p^o = 0.1 MPa) molar enthalpy of formation, in the liquid phase, Δ_fH_m^o(l), and the standard molar enthalpy of vaporization, at T = 298.15 K, Δ_l^gH_m^o, of the methyl 1-methyl-2-pyrrolecarboxylate (M1M2PC). These experiments allowed the determination of its standard (p^o = 0.1 MPa) molar enthalpy of formation, in the gaseous phase, Δ_fH_m^o(g) = −(270.3 ± 2.2) kJ · mol⁻¹, at T = 298.15 K. Additionally, the standard molar enthalpy of formation of M1M2PC was estimated by computations based on standard ab initio molecular calculations at the G3(MP2)//B3LYP level. The estimated values are in very good agreement with experimental one, giving us support to estimate the gas-phase enthalpies of formation of the methyl 1-methyl-3-pyrrolecarboxylate (M1M3PC), ethyl 1-methyl-2-pyrrolecarboxylate (E1M2PC) and ethyl 1-methyl-3-pyrrolecarboxylate (E1M3PC), that were not studied experimentally. The molecular structures of the four molecules were established and the structural parameters were determined at the B3LYP/6-31G(d) level of theory. Furthermore, all the results were interpreted in terms of enthalpic increments

[en] Highlights: • Experimental and computational thermochemical study of 1,2,5-trimethylpyrrole. • Δ_fH_m^o (g) derived from Δ_fH_m^o (l) and Δ_l^gH_m^o. • Δ_fH_m^o(g) estimated for di-, tri-, tetra- and pentamethyl- pyrroles by G3(MP2)//B3LYP method. • New value for the Δ_fH_m^o of 2,5-dimethylfuran. - Abstract: In this work, the 1,2,5-trimethylpyrrole was investigated by combining experimental (static bomb combustion calorimetry and high temperature Calvet microcalorimetry) and computational thermochemical (standard ab initio molecular calculations) results. The experimental value obtained for its standard (p° = 0.1 MPa) molar enthalpy of formation, in the gaseous phase, Δ_fH_m^o(g) = (34.6 ± 2.6) kJ · mol⁻¹, at T = 298.15 K, is in excellent agreement with the estimated data obtained at the G3(MP2)//B3LYP level using a set of gas-phase working reactions. Thereby, these calculations were further extended to estimate the gas-phase enthalpies of formation of all the di-, tri-, tetra- and pentamethylpyrrole derivatives, whose experimental value is not known. Moreover, a new value for the gas-phase molar enthalpy of formation of 2,5-dimethylfuran, as −120.2 kJ · mol⁻¹, determined with the G3(MP2)//B3LYP composite approach, is suggested

[en] The standard (p^compfn=0.1 MPa) molar enthalpies of formation of the crystalline complexes bis[N-(N'',N''-diethylaminothiocarbonyl)benzamidinato]nickel(II), {Ni(datb)₂}, and bis[N-(N'',N''-diethylaminothiocarbonyl)-N^'-phenylbenzamidinato]nickel(II), {Ni(datpb)₂}, were determined, at T=298.15 K, by high precision solution-reaction calorimetry. From the obtained results, the metal-ligand exchange enthalpies in the crystalline phase were derived. The enthalpy of a hypothetical metal-ligand exchange reaction in the crystalline phase was derived, thus allowing a discussion of the energetics of complexation in comparison with known crystal-structural parameters

[en] Highlights: • Δ_cH_m^° of two methyl-5,6-dihydrouracils have been determined by combustion calorimetry. • Vapor pressures were measured by the Knudsen effusion technique. • Gas phase enthalpies of formation of methyl-5,6-dihydrouracils, have been derived. -- Abstract: The standard (p° = 0.1 MPa) molar enthalpy of combustion, Δ_cH_m^°, of two crystalline compounds, 5,6-dihydro-5-methyluracil and 5,6-dihydro-6-methyluracil, were determined, at T = 298.15 K, using a static bomb combustion calorimeter. The vapor pressures as a function of the temperature were measured for those compounds, by the Knudsen effusion technique, and the standard molar enthalpies of sublimation at the mean temperature of the vapor pressure measurements were derived from the Clausius–Clapeyron equation, and corrected to T = 298.15 K using an estimated value for Δ_cr^gC_p,m^°. These values were used to derive the standard molar enthalpies of formation of the two compounds studied, in the condensed and gaseous phases. Some considerations about the relative stability of the two isomers were made and compared with similar compounds

[en] Highlights: • A calorimetric study of bromoacetophenone isomers was performed. • Enthalpies of formation were derived by rotating-bomb combustion calorimetry. • Enthalpies of phase transition were determined by Calvet microcalorimetry. • Cox scheme was applied for the estimation of Δ_fH_m^o (g) for the compounds. • The values of Δ_fH_m^o (g) were compared with literature values for similar compounds. - Abstract: The standard (p^o = 0.1 MPa) molar enthalpies of formation of 2-, 2′-, 3′- and 4′-bromoacetophenones were derived from the standard molar energies of combustion in oxygen, to yield CO₂ (g) and HBr·600H₂O (l) at T = 298.15 K, measured by rotating bomb combustion calorimetry. The standard molar enthalpies associated with phase transitions of the isomers studied at T = 298.15 K, were obtained by high temperature Calvet microcalorimetry. The standard (p^o = 0.1 MPa) molar enthalpies of formation of all the bromoacetophenone isomers in the gaseous phase at T = 298.15 K were derived from the experimental results. The gas-phase enthalpies of formation were also estimated by the empirical scheme developed by Cox and the values obtained were compared with the experimental ones. The results are interpreted in terms of the energetic increments for the introduction of the substituents in the benzene ring

[en] The Knudsen mass-loss effusion technique was used to measure the vapour pressures at different temperatures of the following 4-n-alkylbenzoic acids: 4-methylbenzoic acid, between 319.68 K and 337.33 K, 4-ethylbenzoic acid, between 321.17 K and 335.25 K, 4-propylbenzoic acid, between 331.16 K and 347.16 K, 4-butylbenzoic acid, between 333.16 K and 349.15 K, 4-pentylbenzoic acid, between 341.16 K and 357.16 K, 4-hexylbenzoic acid, between 347.08 K and 363.14 K, 4-heptylbenzoic acid, between 353.16 K and 369.20 K and 4-octylbenzoic acid, between 356.67 K and 371.86 K. From the temperature dependence of the vapour pressure of the crystalline compounds, the standard, p⁰=10⁵ Pa, molar enthalpies, entropies and Gibbs energies of sublimation at T=298.15 K, were derived. A d.s.c. study of the crystalline polymorphic transitions, fusion and isotropization of liquid crystals is also presented

[en] The standard (p⁰=0.1 MPa) molar enthalpies of combustion, in oxygen, of three crystalline N-thiocarbamoylbenzamidines, PhCRNCSNEt₂, R=-NH₂ (DATB), -NEt₂ (DATDB), -NHPh (DATPB), were measured at T=298.15 K by rotating bomb calorimetry. The standard molar enthalpies of sublimation of the three compounds were measured by Calvet microcalorimetry. These values were used to derive the standard molar enthalpies of formation of the compounds in their crystalline and gaseous phases, respectively