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

An extensive thermodynamic study of N-methylformamide (CAS RN: 123-39-7) and N,N-dimethylformamide (CAS RN: 68-12-2), is presented in this work. The liquid heat capacities of N-methylformamide were measured by Tian-Calvet calorimetry in the temperature interval (250-300) K. The vapor pressures for N-methylformamide and N,N-dimethylformamide were measured using static method in the temperature range 238 K to 308 K. The ideal-gas thermodynamic properties were calculated using a combination of the density functional theory (DFT) and statistical thermodynamics. A consistent thermodynamic description was developed using the method of simultaneous correlation, where the experimental and selected literature data for vapor pressures, vaporization enthalpies, and liquid phase heat capacities and the calculated ideal-gas heat capacities were treated together to ensure overall thermodynamic consistency of the results. The resulting vapor pressure equation is valid from the triple point to the normal boiling point temperature.

• Klíčová slova
• N,N-dimethylformamide, N-methylformamide, heat capacity, liquid phase, 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

We present a novel force field model of 2,2,2-trifluoroethanol (TFE) based on the generalized AMBER force field. The model was exhaustively parametrized to reproduce liquid-state properties of pure TFE, namely, density, enthalpy of vaporization, self-diffusion coefficient, and population of trans and gauche conformers. The model predicts excellently other liquid-state properties such as shear viscosity, thermal expansion coefficient, and isotropic compressibility. The resulting model describes unexpectedly well the state equation of the liquid region in the range of 100 K and 10 MPa. More importantly, the proposed TFE model was optimized for use in combination with the TIP4P/Ew and TIP4P/2005 water models. It does not manifest excessive aggregation, which is known for other models, and therefore, it is supposed to more realistically describe the behavior of TFE/water mixtures. This was demonstrated by means of the Kirkwood-Buff theory of solutions and reasonable agreement with experimental data. We explored a considerable part of the parameter space and systematically tested individual combinations of parameters for performance in combination with the TIP4P/Ew and TIP4P/2005 water models. We observed ambiguity in parameters describing pure liquid TFE; however, most of them failed for TFE/water mixtures. We clearly demonstrated the necessity for balanced TFE-TFE, TFE-water, and water-water interactions which can be acquired only by employing implicit polarization correction in the course of parametrization.

• MeSH
• chemické modely MeSH
• difuze MeSH
• lipidy chemie   MeSH
• plyny chemie   MeSH
• rozpouštědla chemie   MeSH
• simulace molekulární dynamiky MeSH
• statická elektřina MeSH
• trifluorethanol chemie   MeSH
• viskozita MeSH
• voda chemie   MeSH
• volatilizace MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• lipidy MeSH
• plyny MeSH
• rozpouštědla MeSH
• trifluorethanol MeSH
• voda MeSH

In this work the breakthrough volumes (BTVs) of volatile organic compounds (VOCs) on Tenax TA were determined in the -10 to 170 degrees C temperature range by using microtrap (MT) technology. The MT technology allowed experimental investigation of the temperature dependence of BTVs. Along with the BTV data, we also discuss the thermodynamics of the temperature dependence of the BTV through a two-parameter equation In (BTV) = A1/T + C1 where T is temperature (K), A1 = -deltaH/R where deltaH is enthalpy of sorption and C1 is constant. This equation fitted well the experimental results with R2 values between 0.9737 (acetone) and 0.9995 (dimethyl disulfide), with n between 6 and 11. However, for n-pentane, n-hexane and 1-hexene it proved that a three parameter equation In (BTV) = A2/ T + BTB + C2 fitted better to the experimental results, with A2 = -deltaHT0/R, B = deltaCp/R, TB = 1n(T/T0) + (T0 - T)/T, C2 a constant, deltaHT0 the adsorption enthalpy at reference temperature T0 and deltaCp the difference in the molar heat capacity of compound under investigation between the sorbed and the free gas phase state. The statistical analysis showed for example for n-pentane now R2 = 0.9969 instead of R2 = 0.9746, and Fisher statistics F = 487 instead of F = 153, with a significance level P = 0.018 for the third parameter. The results show that microtrap technology well serves as a technology to get information on temperature dependence of BTVs in an extended range. Simultaneously, it turns out that MT technology, extending the operational temperature range, is well served by a careful investigation of the temperature dependence models of BTVs.

• MeSH
• organické látky analýza   MeSH
• teplota MeSH
• volatilizace MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• organické látky MeSH

A computational methodology for calculation of sublimation enthalpies of molecular crystals from first principles is developed and validated by comparison to critically evaluated literature experimental data. Temperature-dependent sublimation enthalpies for a set of selected 22 molecular crystals in their low-temperature phases are calculated. The computational methodology consists of several building blocks based on high-level electronic structure methods of quantum chemistry and statistical thermodynamics. Ab initio methods up to the coupled clusters with iterative treatment of single and double excitations and perturbative triples correction with an estimated complete basis set description [CCSD(T)/CBS] are used to calculate the cohesive energies of crystalline phases within a fragment-based additive scheme. Density functional theory (DFT) calculations with periodic boundary conditions (PBC) coupled with the quasi-harmonic approximation are used to evaluate the thermal contributions to the enthalpy of the solid phase. The properties of the vapor phase are calculated within the ideal-gas model using the rigid-rotor harmonic-oscillator model with correction for internal rotation using a one-dimensional hindered rotor approximation and a proper treatment of the molecular rotational degrees of freedom in the vicinity of 0 K. All individual terms contributing to the sublimation enthalpy as a function of temperature are discussed and their uncertainties estimated by comparison to critically evaluated experimental data.

• Publikační typ
• časopisecké články MeSH

Knowledge of the vapor-liquid equilibrium (VLE) properties of molten salts is important in the design of thermal energy storage systems for solar power and nuclear energy production applications. The high temperatures involved make their experimental determination problematic, and the development of both macroscopic thermodynamic correlations and predictive molecular-based methodologies are complicated by the requirement to appropriately incorporate the chemically reacting vapor-phase species. We derive a general thermodynamic-based atomistic simulation framework for molten salt VLE prediction and show its application to NaCl. Its input quantities are temperature-dependent ideal-gas free energy data for the vapor phase reactions and density and residual chemical potential data for the liquid. If these are not available experimentally, the former may be predicted using standard electronic structure software, and the latter may be predicted by means of classical atomistic simulation methodology. The framework predicts the temperature dependence of vapor pressure, coexisting phase densities, vapor phase composition, and vaporization enthalpy. It also predicts the concentrations of vapor phase species present in minor amounts (such as the free ions), quantities that are extremely difficult to measure experimentally. We furthermore use the results to obtain an approximation to the complete VLE binodal dome and the critical properties. We verify the framework for molten NaCl, for which experimentally based density and chemical potential data are available in the literature. We then apply it to the analysis of NaCl simulation data for two commonly used atomistic force fields. The framework can be readily extended to molten salt mixtures and to ionic liquids.

• Publikační typ
• časopisecké články MeSH

Low volatility of ionic liquids (ILs), being one of their most valuable properties, is also the principal factor making reliable measurements of vapor pressures and vaporization (or sublimation) enthalpies of ILs extremely difficult. Alternatively, vaporization enthalpies at the temperature of the triple point can be obtained from the enthalpies of sublimation and fusion. While the latter can be obtained calorimetrically with a fair accuracy, the former is in principle accessible through ab initio computations. This work assesses the performance of the first-principles calculations of sublimation properties of ILs. Namely, 3 compounds, coupling the 1-ethyl-3-methylimidazolium cation [emIm] with either tetrafluoroborate [BF4], hexafluorophosphate [PF6], or bis(trifluoromethylsulfonyl)imide [NTf2] anions were selected for a case study. A computational methodology, originally developed for molecular crystals, is adopted for crystals of ILs. It exploits periodic density functional theory (DFT) calculations of the unit-cell geometries and quasi-harmonic phonons and many-body expansion schemes for ab initio refinements of the lattice energies of crystalline ILs. The vapor phase is treated as the ideal gas whose properties are obtained combining the rigid rotor-harmonic oscillator model with corrections from the one-dimensional hindered rotors and molecular-dynamics simulations capturing the contributions from the interionic interaction modes. Although the given computational approach enables one to reach the chemical accuracy (4 kJ mol-1) of calculated sublimation enthalpies of simple molecular crystals, reaching the same level of accuracy for ionic liquids proves challenging as crystals of ionic liquids are bound appreciably stronger than common molecular crystals, the underlying cohesive energies of solid ionic liquids is up to 1 order of magnitude larger. Still, combination of the mentioned computational and experimental frameworks results in a novel promising scheme that is expected to generate reliable and accurate temperature-dependent data on sublimation (and vaporization) of ILs.

• Publikační typ
• časopisecké články MeSH

Two popular thermodynamic modeling frameworks, namely, the PC-SAFT equation of state and the COSMO-RS model, are benchmarked for their performance in predicting the thermodynamic properties of pure ionic liquids (ILs) and the solubility of CO2 in ILs. The ultimate goal is to provide an illustration of what to expect from these frameworks when applied to ILs in a purely predictive way with established parametrization approaches, since the literature generally lacks their mutual comparisons. Two different modeling approaches with respect to the description of the molecular structure of ILs are tested within both models: a cation-anion pair as (i) a single electroneutral supermolecule and (ii) a pair of separately modeled counterions (ion-based approach). In general, we illustrate that special attention should be paid when estimating unknown thermodynamic data of ILs even with these two progressive thermodynamic frameworks. For both PC-SAFT and COSMO-RS, the supermolecule approach generally yields better results for the vapor pressure and the vaporization enthalpy of pure ILs, while the ion-based approach is found to be more suitable for the solubility of CO2. In spite of some shortcomings, COSMO-RS with the supermolecule approach shows the best overall predictive capabilities for the studied properties. The ion-based strategy within both models has significant limitations in the case of the vaporization properties of ILs. In COSMO-RS, these limitations can, to a certain extent, be surpassed by additional quantum mechanical calculations of the ion pairing in the gas phase, while the ion-based PC-SAFT approach still needs a sophisticated improvement to be developed. As an initiating point, we explore one possible and simple route considering a high degree of cross associations between the counterions in the gas phase.

• MeSH
• anionty chemie   MeSH
• iontové kapaliny * chemie   MeSH
• oxid uhličitý MeSH
• rozpustnost MeSH
• termodynamika MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• anionty MeSH
• iontové kapaliny * MeSH
• oxid uhličitý MeSH

This work presents a molecular dynamics simulation study concerning the thermodynamic data of ionic liquids (ILs) including phase change enthalpies, liquid phase densities, radial and spatial distribution functions, and diffusive properties. Three homologous series of ILs were selected for this study, namely, 1-alkyl-3-methylimidazolium tetrafluoroborates, hexafluorophosphates, and 1,1,2,2-tetrafluoroethanesulfonates, so that properties of 36 ILs are calculated in total. The trends of calculated properties are compared to available experimental data and thoroughly discussed in context of the homologous series. The calculated trends of the vaporization enthalpies within the series are supported by analyzing the structural properties of the ILs. An excellent agreement of calculated structural properties (liquid phase density) with the experimental counterparts is reached. The calculated enthalpic properties are overestimated considerably; thus, further development of the force fields for ILs is required.

• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH