enthalpy and entropy
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Baricitinib is a drug used for the treatment of rheumatoid arthritis. It is a selective and reversible inhibitor of Janus kinases 1 and 2, which play an important role in signalling the pro-inflammatory pathway activated in autoimmune disorders such as rheumatoid arthritis. The pH-spectrophotometric and pH-potentiometric titrations allowed the measurement of three or four successive dissociation constants of Baricitinib. Baricitinib neutral LH2 molecule was able to protonate into two soluble cations LH42+, LH3+ and dissociate into two soluble anions LH- and L2- in pure water. The graph of molar absorption coefficients of differently protonated species versus wavelength indicated that the spectra εL, εLH, εLH2 were the nearly the same for these species and that the spectra εLH4 and εLH3 were also similar. In the pH range from 2-13, four pKa´s of spectra analysis were reliably estimated by REACTLAB at I =0.0020 mol. dm-3 values pKTa1 = 3.07, pKTa2 = 3.87, pKTa3 = 6.27, pKTa4 = 12.78 at 25 °C and pKTa1 = 3.00, pKTa2 = 3.79, pKTa3 = 6.12, pKTa4 = 12.75 at 37 °C. Potentiometric pH-titration analysis for a higher concentration of 1 × 10-3 mol. dm-3 estimated with ESAB at I =0.0001 mol. dm-3 values pKTa1 = 3.69, pKTa2 = 3.81, pKTa3 = 4.73 at 25 °C and pKTa1 = 3.62, pKTa2 = 3.73, pKTa3 = 4.43 at 37 °C. Molar enthalpy ΔH°, molar entropy ΔS° and Gibbs free energy ΔG° were calculated from the spectra using a dependence ln K to 1/T.
- Klíčová slova
- Baricitinib, Dissociation constants, ESAB, REACTLAB, SQUAD84, Spectrophotometric titration, pH-titration,
- MeSH
- azetidiny * MeSH
- entropie MeSH
- koncentrace vodíkových iontů MeSH
- puriny MeSH
- pyrazoly MeSH
- sulfonamidy MeSH
- termodynamika MeSH
- Publikační typ
- časopisecké články MeSH
- Názvy látek
- azetidiny * MeSH
- baricitinib MeSH Prohlížeč
- puriny MeSH
- pyrazoly MeSH
- sulfonamidy MeSH
We study hydrogen bond (HB) redistribution in mixtures of two protic ionic liquids (PILs) sharing the same cation: triethylammonium methanesulfonate ([TEA][OMs]) and triethylammonium trifluoromethanesulfonate ([TEA][OTf]). The mixtures exhibit large negative energies of mixing. Based on results obtained from atomic detail molecular dynamics (MD) simulations, we derive a lattice model, discriminating between HB and nonspecific intermolecular interactions. We demonstrate that due to the ordered structure of the PILs, mostly the HB interactions contribute to the mixing energy. This allows to us to connect the equilibrium of HBs to each of the two anion species with the corresponding excess energies and entropies. The entropy associated with HB redistribution is shown to be negative, and even overcompensating the positive entropy associated with a statistical distribution of the ions in the mixture. This is strongly suggesting that the mixing process is driven by enthalpy, not entropy.
- Publikační typ
- časopisecké články MeSH
The role of entropy in materials science is demonstrated in this report in order to establish its importance for the example of solute segregation at the grain boundaries of bcc iron. We show that substantial differences in grain boundary chemistry arise if their composition is calculated with or without consideration of the entropic term. Another example which clearly documents the necessity of implementing the entropic term in materials science is the enthalpy-entropy compensation effect. Entropy also plays a decisive role in the anisotropy of grain boundary segregation and in interface characterization. The consequences of the ambiguous determination of grain boundary segregation on the prediction of materials behavior are also briefly discussed. All the mentioned examples prove the importance of entropy in the quantification of grain boundary segregation and consequently of other materials properties.
- Klíčová slova
- entropy, grain boundaries, materials properties, solute segregation, thermodynamics,
- 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
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
Elution and solvation processes in liquid chromatography may be controlled by temperature changes. In the case of solvent adsorption, the temperature influences the amount of adsorbed solvent as well as the enthalpy and entropy of the solvation process. In this work, the thermodynamic parameters of organic solvents used as organic modifiers in the reversed-phase high-performance liquid chromatography elution process were determined. The changes of enthalpy and entropy in a series of chemically bonded stationary phases were measured to determine the effects of the temperature and surface coverage density of octadecyl ligands on the thermodynamic parameters of the solvation. For both the enthalpy and entropy a parabolic trend was observed with the minimum for medium surface coverage. The correlation of solvent adsorption values with the enthalpy of solvation was also investigated. The highest influence of the temperature on solvation process was observed for stationary phases with high surface coverage.
- Klíčová slova
- Column liquid chromatography, Enthalpy, Entropy, Solvent adsorption, Temperature influence,
- Publikační typ
- časopisecké články MeSH
In this work, we report a detailed investigation on the factors affecting the in-plane motion of tetrafluoro-1,4-benzoquinone (TFBQ) within a series of charge-transfer (CT) cocrystals formed with various fused aromatic donors. Six crystalline materials were obtained, including four cocrystals, a polymorph, and a solid solution. These were characterized by single-crystal X-ray diffraction (SC XRD), solid-state NMR, FTIR, UV-Vis spectroscopy, and DFT calculations. All cocrystals exhibited short π-stacking interactions and varied noncovalent interactions (NCI) modulating the in-plane motion of TFBQ. 19F T₁ relaxation measurements allowed the quantification of the activation enthalpies (ΔH‡) and entropies (ΔS‡), with theoretical calculations backing these results. Cocrystal 4 is the solid with the most restricted motions due to the presence of strong hydrogen bonds. In contrast, cocrystal 3a depicts the highest in-plane motional frequencies (up to 2.2 MHz at 300 K), owing to the weak contacts around TFBQ. Surprisingly, a solid solution (5), which resembled a mixture of cocrystals 2 and 3a, displayed no significant in-plane motions, despite having similar packing and relaxation behavior to the binary cocrystals. This work illustrates how subtle variations in donor structure affect the in-plane motions and photophysical properties of CT cocrystals, providing valuable insight into the rational design of functional materials.
- Klíčová slova
- 19F T1 relaxation, CT cocrystals, TFBQ, enthalpy and entropy, tunning,
- Publikační typ
- časopisecké články MeSH
HYPOTHESIS: The intricate entropy-enthalpy interplay of dendrimers confined in pores affects their conformation and retention in the porous stationary phase. This work aims at providing important insights into its impacts on partitioning and chromatographic separation in both size-exclusion chromatography (SEC) and interaction chromatography (IC) regimes. SIMULATIONS: Using Monte Carlo (MC) simulations, we investigated the bulk-pore phase equilibria and the conformational behavior of flexible dendrimers differing in generation, in spacer length and in fraction of modified terminal groups interacting differently with pore walls than the majority building units. FINDINGS: With increasing interaction strength, a distinct transition from a roughly spherical shape caused by simultaneous interactions with two walls to an ellipsoidal (or even disklike) conformation tenaciously adhering to only one wall was observed for moderately confined dendrimers. The strongly deformed dendrimers subjected to severe confinement gain high energy and the samples differing in the degree of modification become chromatographically discernable thanks to large energy differences. Consequently, our results suggest that the column fillings with fairly narrow pores which are ineffective in SEC, are highly efficient separation media for dendrimer studies by IC above the critical adsorption point (CAP). Overall, our simulations reveal useful information for advancing and optimizing experimental liquid chromatography studies of dendrimers.
- Klíčová slova
- Chromatography, Confinement, Dendrimer, Enthalpy, Entropy, Monte Carlo simulation, Phase equilibrium, Terminal group,
- MeSH
- dendrimery * MeSH
- metoda Monte Carlo MeSH
- molekulární konformace MeSH
- poréznost MeSH
- termodynamika MeSH
- Publikační typ
- časopisecké články MeSH
- Názvy látek
- dendrimery * MeSH
The chromatographic behavior of steroid hormones on four cholesterol-bonded stationary phases with different structures in binary methanol/water mobile phases was studied. Of the stationary phases tested, the commercially available stationary phases Cogent UDC cholesterol™ and COSMOSIL cholester™ provided better separations of steroid hormones in comparison to homemade aminocholesterol and diaminocholesterol stationary phases. The results show that the temperature has a significant influence on the retention and selectivity for steroid hormones separation. The temperature increase may cause changes in the elution order. From the dependences of the retention (ln k) on temperature (1/T), the standard partial molar enthalpy and standard partial molar entropy were calculated and their enthalpic and entropic contributions to the retention were compared. The enthalpic effects principally control the retention mechanism.
- Klíčová slova
- Cholesterol-bonded phase, Enthalpy, Entropy, Retention, Steroid hormones,
- MeSH
- cholesterol chemie MeSH
- methanol chemie MeSH
- pohlavní steroidní hormony izolace a purifikace MeSH
- termodynamika MeSH
- voda chemie MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
- srovnávací studie MeSH
- Názvy látek
- cholesterol MeSH
- methanol MeSH
- pohlavní steroidní hormony MeSH
- voda MeSH
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
