Journal of Chemical Thermodynamics最新文献

The laser monitoring method was used to assess the solubility of 2-Anilino-6-(dibutylamino)-3-methylfluoran (ODB-2) in four binary solvent systems (methyl acetate, ethyl acetate, n-propyl acetate, n-butyl acetate + acetonitrile) at temperatures ranging from 283.15 K to 323.15 K. The results indicated that the solubility of ODB-2 increased with the increasing temperature and molar fraction of the ester solvent. Five models, including the Apelblat model, λh model, CNIBS/R-K model, Ma model, and Sun model, were applied to fit the experimental ODB-2 solubility data. Among these models, the Apelblat model and CNIBS/R-K model performed significantly better than the other models. Moreover, it was found that the Hansen solubility parameter played a significant role in explaining the dissolving behavior of ODB-2 in the four binary solvents. The intermolecular interactions between solute and solvent, as well as between solvent molecules themselves, were studied using the radial distribution function obtained through molecular dynamics simulations. The findings suggested that the dissolving behavior of ODB-2 was closely related to the intermolecular forces among solute–solvent and solvent–solvent. The thermodynamic properties of the dissolution process, including enthalpy and entropy changes, were calculated using the modified van't Hoff equation. These results demonstrated that the dissolution of ODB-2 was an endothermic process driven by entropy.

Based on pH-metric measurements, the equilibrium constants for ammonia protonation at 298.15 K and ionic strengths I = 5–9, supported by ammonium nitrate, were calculated. Using direct calorimetric measurements, the enthalpies of this process were determined at 288.15, 298.15 and 303.15 K and I = 5–9 and its full thermodynamic parameters were calculated. The sharp increase in exothermicity and decrease in entropy of this process observed at high ionic strengths are explained by decrease in the contribution of desolvation of reagents in the region of deficiency of solvent molecules and the influence of association of ions of background electrolyte. The obtained thermodynamic characteristics of ammonia protonation clearly indicate that a change in solvation state of reaction participants at high ionic strengths changes the nature of this reaction.

Solid solution of rhomboclase [nominally (H₃O) Fe(SO₄)₂·3H₂O] with Fe-In substitution was synthesized by coprecipitation and hydrothermal treatment and investigated by chemical, X-ray diffraction, and thermodynamic analysis in this study. The solid solution is continuous over the whole stoichiometric range despite significant differences in ionic radii between Fe³⁺ and In³⁺. Enthalpy of formation of rhomboclase and enthalpies of mixing of solid solution rhomboclase – indium-substituted rhomboclase were determined by acid-solution calorimetry in 5 mol$·$dm⁻¹ HCl at T = 298.15 K and p = 1 bar. The actual compositions of the studied synthetic end members are (H₃O)_0.798Fe(SO₄)_1.899·3.078H₂O (rhomboclase with molecular mass of 308.8719 g$·$mol⁻¹) and (H₃O)_1.067In(SO₄)_2.034·3.017H₂O (indium-substituted rhomboclase with molecular mass of 384.8377 g$·$mol⁻¹). The enthalpies of mixing were obtained for a series of four indium-incorporating rhomboclase synthetic samples with molar In/(In + Fe) ratios of 0.115, 0.226, 0.537, and 0.733. The enthalpy of formation from elements in their standard state at T = 298.15 K and p = 1 bar obtained in this study by thermochemical cycle for (H₃O)_0.798Fe(SO₄)_1.899·3.078H₂O is: ${\Delta }_f{H}_{298.15}°=-2815.2\pm 2.8$ kJ$·$mol⁻¹. Mean measured enthalpies of dissolution for (H₃O)_0.798Fe(SO₄)_1.899·3.078H₂O and (H₃O)_1.067In(SO₄)_2.034·3.017H₂O are: ${\Delta }_{\mathrm{diss}}H°=14.47\pm 0.42$ kJ$·$mol⁻¹ and $-6.68\pm 0.27$ kJ $·$ mol⁻¹, respectively. Enthalpies of mixing${\Delta }_{\mathrm{mix}}H°$ have small positive values and can be fitted by a regular solid solution model with a mixing parameter $W=4.26\pm 0.32$ kJ$·$mol⁻¹.

To examine the fundamental physicochemical properties as well as intermolecular interactions for the 2-methoxyethanol (EGME) (1) + ethylenediamine (EDA) (2) binary system, this work systemically measured the density ($\rho$) and viscosity ($\eta$) values of the binary system with various mole ratios at P = 100.5 kPa and T = (298.15–318.15) K with the growth gap of 5 K. The as-measured values of the pure substances were compared with literature data. Multiple semi-empirical formulas were used to fit $\rho$ and η values, and the absolute average deviations (AAD%) were calculated. After that, the excess molar volume (${\text{V}}_{\text{m}}^{\text{E}}$), partial molar volume ($\overline{V}$), apparent molar volume (${\text{V}}_{\phi }$), viscosity deviation ($\Delta \text{η}$), excess activation of Gibbs free energy ($\Delta G^{\ast E}$), and several thermodynamic properties of the binary system were systemically analyzed. According to analysis results, it has been proven that the interaction exists between EGME and EDA molecules. And then, excess properties were fitted to the Redlich-Kister equation using multi-parametric nonlinear regression analyses, and standard deviations ($\sigma$) were calculated. In addition, based on various characterization methods including Raman, ultraviolet (UV), and nuclear magnetic resonance hydrogen (¹H NMR) spectral analyses and density functional theory (DFT) calculation results, it is demonstrated that there is intermolecular hydrogen bonds in EGME (1) + EDA (2) binary system as the form of –OH⋯NH₂–, which was consistent with the existence forms of intermolecular hydrogen bonds in different alcohol-amine systems from references. Finally, CO₂ absorption capacity by pure EDA, pure EGME, and the EGME (1) + EDA (2) binary system were severally determined.

Dicyandiamide (DCD) is an important chemical raw material. The solid–liquid equilibrium solubility of DCD in three kinds of binary solvent mixtures (N,N-dimethylformamide (DMF) + ethanol, DMF + acetonitrile, DMF + acetone) at T = (283.15–323.15) K was determined by gravimetric method. The thermodynamic parameters of DCD dissolution in solvents were studied. The solubility of DCD in the three groups of binary mixed solvents increases with the increase of temperature. In three binary mixed solvents, the solubility of DCD increases monotonically with the increase of DMF composition. The modified Apelblat model, van’t Hoff model, λh model, the nonrandom two-liquid (NRTL) model and the Apelblat-Jouyban-Acree model were used to correlate the solubility data. The results show that the modified Apelblat model have the best correlation with the solubility of DCD. The calculation of thermodynamic parameters during the dissolution process indicates that dissolution is exothermic and driven by both enthalpy and entropy. This work can provide reference for improving the crystallization process of DCD, as well as for improving the chemical production process using DCD as raw material.

The gas phase standard enthalpies of formation $\left({\Delta }_f{H}_{\mathrm{gas}}^{°}\right)$ for the tautomers and rotamers of 2- and 8-hydroxy azaazulene and their mercapto analogues have been estimated at B3LYP/6–311 + G(d,p) and M06-2X/6–311++G(2d,2p) levels of theory. The G3MP2 composite method has also been utilized to obtain more accurate correlated computational results. By using atomization and isodesmic reactions, it has been possible to calculate the theoretical enthalpies of formation for the structures under study. Depending on the enthalpies of formation results, the stability of the examined tautomers and rotamers has been discussed. The gas-phase basicity (GB), proton affinities (PA) of the N and O/S atoms, and the deprotonation enthalpies (DPE) of the NH and OH/SH bonds for the investigated system have been determined at the three levels of theory as well.

In order to recover and reuse pure refrigerants from the mixtures used in waste refrigeration facility, it is necessary to find a good way for separation. Due to the extremely low vapor pressure and good selectivity, ionic liquids (ILs) are regarded as promising entrainers for the extractive separation process of azeotropic or near-azeotropic mixtures. Phase behavior of refrigerant with ILs is the basic property in the design of selective absorption-separation process. In this work, the solubility of 3,3,3-trifluoropropene (R-1243zf) and ethyl fluoride (R-161) with trihexyltetradecylphosphonium chloride ([P_6,6,6,14][Cl]) were measured based on the isochoric saturation method. The experimental temperature range was from 283.15 K to 343.15 K. Five activity coefficient models, including Margules, van Laar, Scatchard-Hamer, Wilson and non-random two-liquid (NRTL) model, were used to correlate the experimental data, and the results were discussed. In addition, based on the literature data, the separation capacities of different ILs for refrigerant blends composed of R-1243zf or R-161 were investigated.

Deep eutectic solvent (DES) shows excellent absorption performance in the field of CO₂ capture. It is considered as a new green absorption solvent to replace monoethanolamine. In the industry, the presence of water not only affects the structural stability of the solvent, but also affects its thermophysical properties. In this work, three kinds of hydrophobic DES were prepared. Based on the study of their structural characteristics and thermal stability, the density and viscosity of DES with water mixture were measured in the temperature range of 298.15 ∼ 338.15 K at atmospheric pressure. It was demonstrated that the trace water did not destroy the structure of DES, but it formed hydrogen bonds with DES. The increase water destroyed the structure of DES and formed hydrogen bonds with hydrogen bond donor (HBD) and hydrogen bond acceptor (HBA), respectively. Moreover, the hard sphere model was applied to study the viscosity, and after introducing the binary interaction parameter, the average absolute relative deviation of the mixture reduced to 4.4 ∼ 7.7 %.

2′,4′-Dichloro-5′-fluoroacetophenone is a key intermediate in the preparation of ciprofloxacin hydrochloride, a broad-spectrum quinolone antibacterial drug. Wherein, crystallization and solid–liquid equilibrium thermodynamics play an irreplaceable role in the separation and purification of 2′,4′-Dichloro-5′-fluoroacetophenone. Therefore, in this work, the solubility of 2′,4′-Dichloro-5′-fluoroacetophenone was measured by dynamic method in eight different solvents and range from 273.15 K to 288.15 K. The results showed that the solubility of 2′,4′-Dichloro-5′-fluoroacetophenone increased with increasing temperature. Further analysis showed that the solubility of 2′,4′-Dichloro-5′-fluoroacetophenone increased with increasing carbon chain length in ester solvents. Single crystals of 2′,4′-Dichloro-5′-fluoroacetophenone were successfully prepared and the result reveals that the Cl⋯H, O⋯H, and F⋯H interactions dominated the packing and long-range order of the crystals. Then, different thermodynamic models were employed to describe the thermodynamic behavior of 2′,4′-Dichloro-5′-fluoroacetophenone. The calculated ARD% and RMSD values show that the correlation results are in good agreement with the experimental data, and the Van’t Hoff equation has the best regression performance. Finally, it is interesting to find that the contribution of entropy and enthalpy change to dissolution of 2′,4′-Dichloro-5′-fluoroacetophenone tends to be equal with increasing temperature.