BACKGROUND: The aim of the current work was to determine thermo dynamical properties of 5(2-nitro phenyl)-furan-2-carbaldehyde, 5(3-nitro phenyl)-furan-2-carbaldehyde and 5(4-nitro phenyl)-furan-2-carbaldehyde. RESULTS: The temperature dependence of saturated vapor pressure of 5(2-nitro phenyl)-furan-2-carbaldehyde, 5(3-nitro phenyl)-furan-2-carbaldehyde and 5(4-nitro phenyl)-furan-2-carbaldehyde was determined by Knudsen's effusion method. The results are presented by the Clapeyron-Clausius equation in linear form, and via this form, the standard enthalpies, entropies and Gibbs energies of sublimation and evaporation of compounds were calculated at 298.15 K. The standard molar formation enthalpies of compounds in crystalline state at 298.15 K were determined indirectly by the corresponding standard molar combustion enthalpy, obtained using bomb calorimetry combustion. CONCLUSIONS: Determination of the thermodynamic properties for these compounds may contribute to solving practical problems pertaining optimization processes of their synthesis, purification and application and it will also provide a more thorough insight regarding the theoretical knowledge of their nature.Graphical abstract:Generalized structural formula of investigated compounds and their formation enthalpy determination scheme in the gaseous state.

• Klíčová slova
• 5(2-Nitrophenyl)-furan-2-carbaldehydes, Combustion enthalpy, Formation enthalpy, Isomerisation enthalpy, Sublimation enthalpy, Vapor pressure, Vaporization enthalpy,
• Publikační typ
• časopisecké články MeSH

BACKGROUND: The aim of the current work was to determine thermodynamical properties of 5-(nitrophenyl)-2-furaldehyde oximes and 3-[5-(nitrolphenyl)-2-furyl]acrylic acids. RESULTS: The temperature dependences of saturated vapor pressures of 5-(nitrophenyl)-2-furaldehyde oximes and 3-[5-(nitrolphenyl)-2-furyl]acrylic acids were determined by the Knudsen effusion method. The results are presented by the Clapeyron-Clausius equation in linear form, and via this form, the standard enthalpies of sublimation of compounds were calculated at 298.15 K. The standard molar formation enthalpies of compounds in crystalline state at 298.15 K were determined indirectly from the corresponding standard molar combustion enthalpy, obtained using combustion bomb calorimetry. The non-nearest neighbour interactions (strain) in molecule were defined. The ideal-gas enthalpies of investigated compounds formation and the data available from the literature were used for calculation of group-additivity parameters and the correction terms useful in the application of the Benson correlation. CONCLUSION: Determining the thermodynamic properties for these compounds will contribute to solving practical problems pertaining to optimization processes of their synthesis, purification and application. It will also provide a more thorough insight regarding the theoretical knowledge of their nature and are necessary for the application of the Benson group-contribution correlation for calculation of Δ f H m ( 298.15 K ) o (g)calc.

• Klíčová slova
• Arylfuran derivatives, Combustion enthalpy, Formation enthalpy, Group-additivity correlation, Isomerization, Sublimation enthalpy, Vapor pressure,
• Publikační typ
• časopisecké články MeSH

Energies of hydrocarbon monoderivatives CH(3)X, C(2)H(5)X, n-C(4)H(9)X, and n-C(5)H(11)X with 16 different substituents X were calculated at the levels B3LYP/6-311+G(d,p) and B3LYP/AUG-cc-pVTZ//B3LYP/6-311+G(d,p). The results were used to test the validity of the additive rule that has served commonly for estimating the enthalpies of formation Delta(f)H(T). The exact additivity corresponds to zero reaction energy DeltaE of the isodesmic reaction, in which the substituent X is transferred from one alkyl group R to another. Additivity is approximately fulfilled for butyl and pentyl derivatives with the differences less than 0.3 kJ mol(-1) (except charged groups X). Methyl derivatives deviated from the additive rule up to 22 kJ mol(-1) for dipolar groups X and 45 kJ mol(-1) for charged group, in agreement with the available experiments and with the anticipation of all suggested empirical schemes. In addition, smaller deviations of ethyl derivatives (3 or 20 kJ mol(-1), respectively) were observed here for the first time. There is no correlation between the deviations of methyl and ethyl derivatives; they are also not related to steric effects, and only partly to polarization. Deviations of methyl derivatives are proportional to the electronegativity of the first atom of the substituent; even when the definition of electronegativity is somewhat questionable, one can say in any case that it is controlled by the first atom.

• Publikační typ
• časopisecké články MeSH

The folding free energy of the INK4c tumor suppressor core, consisting of 10 helices, was determined as the sum of gas-phase interaction enthalpy, gas-phase interaction entropy, and dehydration and hydration free energy. The interaction energy and the hydration free energy were determined using the nonempirical density functional theory (DFT) method, augmented by a dispersion-energy correction term, the semiempirical density-functional tight-binding method covering the dispersion energy, and the density functional theory/conductor-like screening model (DFT/COSMO) procedure, whereas the interaction entropy was calculated with the empirical Cornell et al. force field. Alternatively, all contributions were evaluated consistently using empirical methods. All the values of the interaction energy of helix pairs are stabilizing, and the dominant stabilizing terms stem from the London dispersion energy and, in the case of charged systems, the electrostatic energy. The stabilization energy of the core, determined as the difference of the energy of the core and 10 separate helices, amounts to approximately 450 kcal/mol. Systematically, the difference in the hydration free energy of a helix pair and its separate components is smaller in magnitude than the interaction energy, and it is negative for some pairs while positive for others. The average total free energy of a core formation amounts to -29.6 kcal/mol (yielded by scaled quantum-chemical methods) and +13.9 kcal/mol (resulting from empirical methods). These values are considerably smaller than their single components, which are dominated by the interaction energy. The computationally predicted interval encloses the experimental value of the folding free energy (-2.8 kcal/mol).

• MeSH
• aminokyselinové motivy MeSH
• inhibitor p16 cyklin-dependentní kinasy chemie   MeSH
• konformace proteinů MeSH
• krystalografie rentgenová MeSH
• kvantová teorie * MeSH
• molekulární modely MeSH
• počítačová simulace MeSH
• rozpouštědla chemie   MeSH
• sbalování proteinů * MeSH
• sekundární struktura proteinů MeSH
• termodynamika MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• inhibitor p16 cyklin-dependentní kinasy MeSH
• rozpouštědla MeSH

Energies of 20 alkyl-substituted benzoic acids were calculated at the levels B3LYP/6-311+G(d,p)//B3LYP/6-311+G(d,p) and MP2/6-311+G(d,p)//MP2/6-311+G(d,p); the pertinent enthalpies at 298 K were calculated at the same levels. Comparison with experimental enthalpies of formation Delta(f)H degrees (g)(298) was carried out in terms of isodesmic reactions, that is, in the relative values. Of the four calculated quantities, the DFT enthalpies yielded best correlation with the standard deviation of 2.1 kJ mol(-1), near to the experimental uncertainty; the DFT energies are only slightly worse and the MP2 enthalpies or energies much worse. However, the DFT method overestimated systematically the substituent effects and had to be calibrated. Comparison with the experimental gas-phase acidities was less telling and the fit was worse because both methods overestimated the substituent effects. Extending the base in selected examples did not give better results. Although the systematic deviations are evidently due to the imperfections of the theoretical models, individual big deviations should be attributed to experimental errors or to the abnormal behavior of certain compounds at the experimental conditions. From this point of view, three examples of the so-called long-range effect claimed in the case of different benzoic acid derivatives, always for substituents in the meta position, must be refused as unproven because the experimental energies were not confirmed by calculations.

• MeSH
• benzoáty * chemická syntéza   chemie   MeSH
• molekulární struktura MeSH
• termodynamika * MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• benzoáty * MeSH

The chalcogenides of p-block elements constitute a significant category of materials with substantial potential for advancing the field of electronic and optoelectronic devices. This is attributed to their exceptional characteristics, including elevated carrier mobility and the ability to fine-tune band gaps through solid solution formation. These compounds exhibit diverse structures, encompassing both three-dimensional and two-dimensional configurations, the latter exemplified by the compound In2Se3. Sesqui-chalcogenides were synthesized through the direct reaction of highly pure elements within a quartz ampoule. Their single-phase composition was confirmed using X-ray diffraction, and the morphology and chemical composition were characterized using scanning electron microscopy. The compositions of all six materials were also confirmed using X-ray photoelectron spectroscopy and Raman spectroscopy. This investigation delves into the thermodynamic properties of indium and gallium sesqui-chalcogenides. It involves low-temperature heat capacity measurements to evaluate standard entropies and Tian-Calvet calorimetry to elucidate the temperature dependence of heat capacity beyond the reference temperature of 298.15 K, as well as the enthalpy of formation assessed from DFT calculations.

• Klíčová slova
• Ga, Gibbs energy, In, enthalpy, entropy, heat capacity, sesqui-chalcogenides,
• Publikační typ
• časopisecké články MeSH

This work aims to describe the mechanism of intermediary phases formation in TiAl20 (wt. %) alloy composition during reactive sintering. The reaction between titanium and aluminum powders was studied by in situ diffraction and the results were confirmed by annealing at various temperatures. It was found that the Ti2Al5 phase formed preferentially and its formation was detected at 400 °C. So far, this phase has never been found in this alloy composition during reactive sintering processes. Subsequently, the Ti2Al5 phase reacted with the titanium, and the formation of the major phase, Ti3Al, was accompanied by the minor phase, TiAl. Equations of the proposed reactions are presented in this paper and their thermodynamic and kinetic feasibility are supported by Gibbs energies of reaction and reaction enthalpies.

• Klíčová slova
• aluminides, in situ diffraction, mechanism, powder metallurgy, reactive sintering,
• Publikační typ
• časopisecké články MeSH

Two proteins, alkaline phosphatase (AP) and cytochrome c (cyt c) which seem to be involved in the apoptotic cell death program were examined on their interaction. Intestinal AP affects ferricytochrome c (cyt c(FeIII)) by changing its optical properties, redox state and conformation. The effect proceeded over the course of hours with a gradual decrease in free cyt c(FeIII) as the AP concentration increased. A heme containing high molecular species was created in the first stage of interaction of the proteins in neutral, acidic (pH 2.6), alkaline (pH 8.3), low ionic strength (10 mmol/l phosphate), and high ionic strength (0.5 mol/l NaCl) media. Further complexation was favored by higher pH values and temperature. Differential scanning calorimetry revealed a decrease in enthalpy of the thermodenaturation temperature (Tm) of cyt c at 84.5 degrees C due to the AP addition. Increments of AP in the mixtures resulted in the appearance of Tm peaks at 68 degrees C and 61 degrees C. Electrophoretic analysis of the commercial samples of intestinal APs showed main fractions from 63.2 kDa to 72.9 kDa and from 172.9 up to 179.0 kDa. Changes in positions and intensities of the bands were detected upon longer incubation (24 h) with cyt c. The electrophoretic pattern of the bacterial AP was homogeneous with one fraction of 43.7 kDa showing no alteration due to the cyt c presence. Gel permeation chromatography of incubated mixtures of intestinal APs and cyt c confirmed the creation of new heme containing complexes.

• MeSH
• alkalická fosfatasa chemie   MeSH
• apoptóza MeSH
• cytochromy skupiny c chemie   MeSH
• denaturace proteinů MeSH
• diferenciální skenovací kalorimetrie MeSH
• elektroforéza v polyakrylamidovém gelu MeSH
• gelová chromatografie MeSH
• koncentrace vodíkových iontů MeSH
• spektrofotometrie ultrafialová MeSH
• vazba proteinů MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• alkalická fosfatasa MeSH
• cytochromy skupiny c MeSH

Y2BaCuO5 often occurs as an accompanying phase of the well-known high-temperature superconductor YBa2Cu3O7 (also known as YBCO). Y2BaCuO5, easily identifiable due to its characteristic green coloration, is often referred to as 'green phase' or 'Y-211'. In this contribution, Y2BaCuO5 phase was studied in detail with a focus on its thermal and thermodynamic properties. Energy dispersive spectroscopy (EDS), X-ray diffraction (XRD), and scanning electron microscopy (SEM) were employed in the study of sample's morphology and chemical composition. XRD data were further analyzed and lattice parameters refined by Rietveld analysis. Simultaneous thermal analysis was employed to study thermal stability. Particle size distribution was analyzed by laser diffraction. Finally, thermodynamic properties, namely heat capacity and relative enthalpy, were measured by drop calorimetry, differential scanning calorimetry (DSC), and physical properties measurement system (PPMS). Enthalpy of formation was assessed from ab-initio DFT calculations.

• Klíčová slova
• Y-211, Y2BaCuO5, YBCO, superconductors, thermodynamic properties,
• Publikační typ
• časopisecké články MeSH

The values of thermochemical quantities (enthalpy and Gibbs energy of formation, entropy and molar heat capacity) in the ideal gas state and dihedral angles for all 209 polychlorinated biphenyls were obtained by the Benson contribution method and ab initio calculations. The di-, tri- and tetra-ortho-chlorinated biphenyls are related with properties of WHO non-ortho- and mono-ortho-biphenyls in connection with their potential human toxicities.

• Publikační typ
• časopisecké články MeSH