Search

© 2016 Elsevier B.V.Ethylene glycol is one of the most usually used liquid media for realization of different industrial processes. In present work thermochemistry of solvation of inert gases and organic solutes in ethylene glycol was thoroughly studied using solution calorimetry technique. Enthalpies of solution of 28 organic solutes in ethylene glycol were measured for the first time. Acree and Abraham multi-parameter correlations were successfully applied for description of enthalpies of solvation of number of inert gases and organic compounds in ethylene glycol calculated on the basis of experimental and literature data. Enthalpies of solute-ethylene glycol hydrogen bonding for some ketones, esters, ethers, nitriles, monoatomic aliphatic alcohols, amines and etc. were determined. Linear correlation between enthalpies of solute-ethylene glycol and solute-methanol hydrogen bonding was observed.

© 2016 American Chemical Society.The enthalpies of formation of 2-, 3-, and 4-CH3-benzamide, as well as for 2-CH3O-benzamide, were measured by using combustion calorimetry. Vapor pressures of the isomeric CH3- and CH3O-benzamides were measured by using the transpiration method. The enthalpies of sublimation/vaporization of these compounds at 298 K were obtained from temperature dependencies of vapor pressures. The enthalpies of solution of the isomeric CH3- and CH3O-benzamides were measured with solution calorimetry. The enthalpies of sublimation of m- and p-substituted benzamides were independently derived with help of a solution calorimetry-based procedure. The enthalpies of fusion of the CH3-benzamides were derived from differential scanning calorimetry measurements. Thermochemical data on CH3- and CH3O-benzamides were collected, evaluated, and tested for internal consistency. A simple incremental procedure was suggested for a quick appraisal of vaporization enthalpies of substituted benzamides. The high-level G4 quantum-chemical method was used for mutual validation of the experimental and theoretical gas-phase enthalpies of formation. A remarkable ability of the G4-based atomization procedure to calculate reliable enthalpies of formation was established for the set of aliphatic and aromatic amides. An outlook for the proper validation of the G4-AT procedure was discussed.

We propose a method for calculating the Gibbs energies of hydrogen bonding of solutes with associated solvents via the thermodynamic analysis of experimental values of solvation Gibbs energies. The method is applied to solutions of different proton acceptors in methanol. It is shown that the contribution of hydrogen bonding processes to the solvation Gibbs energy in methanol is in most cases very different in magnitude from the formation Gibbs energy of equimolar complexes of the solute and methanol. We demonstrate the need to include the contributions from solvophobic effects in investigating intermolecular interactions in associated solvents by means of thermodynamic data. © 2011 Pleiades Publishing, Ltd.

Reactivity and equilibrium properties of organic molecules in self-associated liquids greatly depend on the hydrogen bonding with solvent. This work contains comprehensive thermodynamic analysis of hydrogen bonding of aliphatic and aromatic amines in self-associated solvent methanol. Enthalpies of solution at infinite dilution and limiting activity coefficients for the studied systems were measured experimentally. Enthalpies and Gibbs energies of hydrogen bonding of amines with neat methanol were determined. These values were found to be decreased compared with hydrogen bond energy in equimolar complexes "methanol-amine" determined in inert solvent or base media. A linear dependence between enthalpies and Gibbs energies of hydrogen bonding of amines with neat methanol was observed. It was firstly revealed that the entropy of specific interactions of amines with neat methanol can be about zero or positive. Disruption of solvent-solvent hydrogen bonds can be regarded as the most important step during dissolution of amine in methanol. It was found that the cooperative effect influences on the Gibbs energies of hydrogen bonding of amines in methanol, but in a lesser extent than in aqueous solutions. The new results show that the hydrogen bonding process in the self-associated solvents differs significantly from equimolar complexation in aprotic media. © 2012 Elsevier B.V. All rights reserved.

The activity coefficients at infinite dilution (T = 298.15 K) and Gibbs energy of solvation of pyridines in aliphatic alcohols were determined. The thermodynamic functions of specific interactions in these systems were calculated. © 2013 Pleiades Publishing, Ltd.

Thermochemistry of hydration of the aliphatic and aromatic amines was studied. Enthalpies of solution at infinite dilution of amines in water were measured using the method of solution calorimetry. A procedure of taking into account the ionization and non-specific hydration of amines in aqueous media was carried out. A method for estimating the enthalpy of hydrogen bonding of amines in aqueous solutions was suggested on the basis of a comparative analysis of the solvation enthalpies of the solutes in water and methanol. The efficiency of this method is confirmed by evaluating the hydrophobic effect enthalpy. © Pleiades Publishing, Ltd., 2012.

© 2015 American Chemical Society. The imidazole structure offers a versatile means of developing molecules with controlled/tunable physicochemical properties that have significant utility in many applications and can be further derivatized to form ionic liquids. In the literature, the vast majority of studies on structure-property relationships in these types of molecules are devoted to linear (e.g., n-alkyl) substituents. However, imidazoles with branched or cycloalkyl groups are equally accessible through convenient synthetic methods - yet there are essentially no reports on the physical properties of such compounds in the literature. Here, the absolute vapor pressures of branched and cycloalkyl derivatives of imidazole have been determined as a function of temperature by the transpiration method. The standard molar enthalpies of vaporization were derived from the temperature dependences of vapor pressures. The measured data sets were successfully checked for internal consistency by comparison with vaporization enthalpies of the parent species, and a group contribution method is put forth by which the vaporization enthalpies of imidazoles, and imidazolium-based ILs, with alkyl groups in any configuration can be rapidly predicted.

© 2014 American Chemical Society. Densities and speeds of sound were measured for binary mixtures of butan-2-one with methanol, propan-1-ol, butan-1-ol, and chloroform at temperatures of 293.15-323.15 K and at atmospheric pressure, with the uncertainties of 0.05 kg·m-3 and 0.5 m·s-1, respectively. The molar excesses of volume, isentropic compression, and thermal expansion were calculated for those systems from the measured speeds and densities and for the mixture of butan-2-one with ethanol from the data reported in the literature. The negative excess volumes for the mixtures with alcohols decrease with the elongation of the hydrocarbon chain, and they eventually become positive for propan-1-ol and butan-1-ol at higher temperatures. That probably reflects the vanishing difference in size of the molecules in the mixture. The excess volume of butan-2-one + chloroform is close to that of butan-2-one + methanol. The excess expansion of butan-2-one + chloroform is negative, and it is positive for butan-2-one + alcohols, while the excess compression isotherms are approximately mirror images of those of the excess expansion. That results probably from the counteracting effects of temperature and pressure on the aggregation due to hydrogen bonds.(Graph Presented).

© 2015 Elsevier Ltd. All rights reserved. The gas-phase enthalpies of formation of 2-, 3-, and 4-methylbenzonitrile at T = 298.15 K were studied by combustion calorimetry, and their vaporization enthalpies were determined using the transpiration method. The composite ab initio methods W1-F12 and G4 were used to calculate the gas-phase enthalpies of formation for these three methylbenzonitriles. These theoretical values were found to be in excellent agreement with the corresponding experimental data. The analysis of these data revealed that the interaction between cyano and methyl groups is slightly stabilizing. Using the experimental data a set of group-additivity terms, which allows to estimate thermochemical properties for methyl and cyano substituted benzenes, was proposed. These terms, together with theoretical data, were subsequently used to reassess the thermochemical properties of 2,6-dimethylbenzonitrile and 2,4,6-trimethylbenzonitrile.

© 2015 Elsevier Ltd. All rights reserved. Accurate standard molar enthalpy of formation values in the liquid phase can be obtained by combining high-level quantum chemistry values of gas-phase enthalpies of formation with experimentally determined enthalpies of vaporisation. The procedure is illustrated for 2-, 3-, and 4-methyl-anisoles. Using the W1-F12 and G4 quantum-chemical methods, the gas-phase enthalpies of formation of these compounds at T = 298.15 K were computed. Molar enthalpies of vaporisation for these isomers were measured by the transpiration method. Combining the experimental and the high-level ab initio values, the standard molar enthalpies of formation in the liquid phase for all three isomers were derived and compared with those determined for 2- and 4-methyl-anisoles by using combustion calorimetry.

The work is devoted to the investigation of thermodynamics of specific interaction of the tertiary aliphatic and aromatic amines with associated solvents as which aliphatic alcohols were taken. Solution enthalpies of aliphatic alcohols in amines (tri-n-propylamine, 2-methylpyridine, 3-methylpyridine, N-methylimidazole) as well as amines in alcohols were measured at infinite dilution. The enthalpies of specific interaction (H-bonding) in systems studied were determined based on experimental data. The enthalpies of specific interaction of amines in aliphatic alcohols significantly lower than the enthalpies of hydrogen bonding in complexes amine-alcohol of 1:1 composition determined in base media due to the reorganization of aliphatic alcohols as solvents. The determination of solvent reorganization contribution makes possible to define the hydrogen bonding enthalpies of amines with clusters of alcohols. Obtained enthalpies of hydrogen bonding in multi-particle complexes are sensitive to the influence of cooperative effect. It was shown, that hydrogen bond cooperativity factors in multi-particle complexes of alcohols with amines are approximately equal for all alcohols when pyridines and N-methylimidazole as solutes are used. At the same time, H-bonding cooperativity factors in complexes of trialkylamines with associative species of alcohols decrease with increasing of alkyl radical length in alcohol and amine molecules. This work shows that the thermodynamic functions of specific interaction of solutes with associated solvents cannot be described using the H-bond parameters for the complexes of 1:1 composition. © 2011 Elsevier Ltd. All rights reserved.

The properties of solutes and their reactivity in aliphatic alcohols significantly depend on the formation of hydrogen bonds. In this work, calorimetric, FTIR-spectroscopic and gas chromatographic vapor pressure studies of hydrogen bonds of weak bases in solution of aliphatic alcohols were carried out. Enthalpies of solutions at infinite dilution of ketones, nitriles and acetates in methanol and octan-1-ol were measured. Obtained from the calorimetric data, the enthalpies of specific interaction of weak bases in aliphatic alcohols unexpectedly found to be positive. IR spectra of solutions of ketones in aliphatic alcohols at infinite dilution were measured at different temperatures. Enthalpies of specific interaction in studied systems obtained from the spectroscopic data confirmed the endothermic process and are in good agreement with calorimetric results. Gibbs energies and entropies of specific interaction of weak bases in aliphatic alcohols were determined. Obtained results show, that the hydrogen bonding process of weak bases in aliphatic alcohols differs substantially from the formation of complexes 1:1 ROH⋯B (B - weak proton acceptor) in aprotic media. The complicated process of hydrogen bonding of weak bases in aliphatic alcohols apparently is controlled by the entropy factor, because these values are above zero. © 2011 Elsevier B.V. All rights reserved.

© 2016 American Chemical Society.The enthalpies of formation of 2-, 3-, and 4-CH3-benzamide, as well as for 2-CH3O-benzamide, were measured by using combustion calorimetry. Vapor pressures of the isomeric CH3- and CH3O-benzamides were measured by using the transpiration method. The enthalpies of sublimation/vaporization of these compounds at 298 K were obtained from temperature dependencies of vapor pressures. The enthalpies of solution of the isomeric CH3- and CH3O-benzamides were measured with solution calorimetry. The enthalpies of sublimation of m- and p-substituted benzamides were independently derived with help of a solution calorimetry-based procedure. The enthalpies of fusion of the CH3-benzamides were derived from differential scanning calorimetry measurements. Thermochemical data on CH3- and CH3O-benzamides were collected, evaluated, and tested for internal consistency. A simple incremental procedure was suggested for a quick appraisal of vaporization enthalpies of substituted benzamides. The high-level G4 quantum-chemical method was used for mutual validation of the experimental and theoretical gas-phase enthalpies of formation. A remarkable ability of the G4-based atomization procedure to calculate reliable enthalpies of formation was established for the set of aliphatic and aromatic amides. An outlook for the proper validation of the G4-AT procedure was discussed.

© 2016 Elsevier B.V.Ethylene glycol is one of the most usually used liquid media for realization of different industrial processes. In present work thermochemistry of solvation of inert gases and organic solutes in ethylene glycol was thoroughly studied using solution calorimetry technique. Enthalpies of solution of 28 organic solutes in ethylene glycol were measured for the first time. Acree and Abraham multi-parameter correlations were successfully applied for description of enthalpies of solvation of number of inert gases and organic compounds in ethylene glycol calculated on the basis of experimental and literature data. Enthalpies of solute-ethylene glycol hydrogen bonding for some ketones, esters, ethers, nitriles, monoatomic aliphatic alcohols, amines and etc. were determined. Linear correlation between enthalpies of solute-ethylene glycol and solute-methanol hydrogen bonding was observed.

© 2015 American Chemical Society. The imidazole structure offers a versatile means of developing molecules with controlled/tunable physicochemical properties that have significant utility in many applications and can be further derivatized to form ionic liquids. In the literature, the vast majority of studies on structure-property relationships in these types of molecules are devoted to linear (e.g., n-alkyl) substituents. However, imidazoles with branched or cycloalkyl groups are equally accessible through convenient synthetic methods - yet there are essentially no reports on the physical properties of such compounds in the literature. Here, the absolute vapor pressures of branched and cycloalkyl derivatives of imidazole have been determined as a function of temperature by the transpiration method. The standard molar enthalpies of vaporization were derived from the temperature dependences of vapor pressures. The measured data sets were successfully checked for internal consistency by comparison with vaporization enthalpies of the parent species, and a group contribution method is put forth by which the vaporization enthalpies of imidazoles, and imidazolium-based ILs, with alkyl groups in any configuration can be rapidly predicted.

© 2014 American Chemical Society. Densities and speeds of sound were measured for binary mixtures of butan-2-one with methanol, propan-1-ol, butan-1-ol, and chloroform at temperatures of 293.15-323.15 K and at atmospheric pressure, with the uncertainties of 0.05 kg·m-3 and 0.5 m·s-1, respectively. The molar excesses of volume, isentropic compression, and thermal expansion were calculated for those systems from the measured speeds and densities and for the mixture of butan-2-one with ethanol from the data reported in the literature. The negative excess volumes for the mixtures with alcohols decrease with the elongation of the hydrocarbon chain, and they eventually become positive for propan-1-ol and butan-1-ol at higher temperatures. That probably reflects the vanishing difference in size of the molecules in the mixture. The excess volume of butan-2-one + chloroform is close to that of butan-2-one + methanol. The excess expansion of butan-2-one + chloroform is negative, and it is positive for butan-2-one + alcohols, while the excess compression isotherms are approximately mirror images of those of the excess expansion. That results probably from the counteracting effects of temperature and pressure on the aggregation due to hydrogen bonds.(Graph Presented).

© 2015 Elsevier Ltd. All rights reserved. Accurate standard molar enthalpy of formation values in the liquid phase can be obtained by combining high-level quantum chemistry values of gas-phase enthalpies of formation with experimentally determined enthalpies of vaporisation. The procedure is illustrated for 2-, 3-, and 4-methyl-anisoles. Using the W1-F12 and G4 quantum-chemical methods, the gas-phase enthalpies of formation of these compounds at T = 298.15 K were computed. Molar enthalpies of vaporisation for these isomers were measured by the transpiration method. Combining the experimental and the high-level ab initio values, the standard molar enthalpies of formation in the liquid phase for all three isomers were derived and compared with those determined for 2- and 4-methyl-anisoles by using combustion calorimetry.

© 2015 Elsevier Ltd. All rights reserved. The gas-phase enthalpies of formation of 2-, 3-, and 4-methylbenzonitrile at T = 298.15 K were studied by combustion calorimetry, and their vaporization enthalpies were determined using the transpiration method. The composite ab initio methods W1-F12 and G4 were used to calculate the gas-phase enthalpies of formation for these three methylbenzonitriles. These theoretical values were found to be in excellent agreement with the corresponding experimental data. The analysis of these data revealed that the interaction between cyano and methyl groups is slightly stabilizing. Using the experimental data a set of group-additivity terms, which allows to estimate thermochemical properties for methyl and cyano substituted benzenes, was proposed. These terms, together with theoretical data, were subsequently used to reassess the thermochemical properties of 2,6-dimethylbenzonitrile and 2,4,6-trimethylbenzonitrile.

Thermochemistry of hydration of the aliphatic and aromatic amines was studied. Enthalpies of solution at infinite dilution of amines in water were measured using the method of solution calorimetry. A procedure of taking into account the ionization and non-specific hydration of amines in aqueous media was carried out. A method for estimating the enthalpy of hydrogen bonding of amines in aqueous solutions was suggested on the basis of a comparative analysis of the solvation enthalpies of the solutes in water and methanol. The efficiency of this method is confirmed by evaluating the hydrophobic effect enthalpy. © Pleiades Publishing, Ltd., 2012.

The activity coefficients at infinite dilution (T = 298.15 K) and Gibbs energy of solvation of pyridines in aliphatic alcohols were determined. The thermodynamic functions of specific interactions in these systems were calculated. © 2013 Pleiades Publishing, Ltd.

The measurements of enthalpies of triethylamine and tri-n-butylamine dissolution in aliphatic alcohols and, vice versa, of aliphatic alcohols in amines were carried out. Enthalpies of specific interactions in the studied systems were calculated. The enthalpy of specific interaction determined in the alcohol medium, are significantly less than those obtained at dissolving alcohols in amines. The mechanism of specific interaction of amines with alcohols is discussed. Enthalpies of cooperative hydrogen bonds of tertiary amines with alcohol clusters are calculated. The dependences between the enthalpies of hydrogen bond and the spatial structure of interacting molecules are revealed. © 2010 Pleiades Publishing, Ltd.

Reactivity and equilibrium properties of organic molecules in self-associated liquids greatly depend on the hydrogen bonding with solvent. This work contains comprehensive thermodynamic analysis of hydrogen bonding of aliphatic and aromatic amines in self-associated solvent methanol. Enthalpies of solution at infinite dilution and limiting activity coefficients for the studied systems were measured experimentally. Enthalpies and Gibbs energies of hydrogen bonding of amines with neat methanol were determined. These values were found to be decreased compared with hydrogen bond energy in equimolar complexes "methanol-amine" determined in inert solvent or base media. A linear dependence between enthalpies and Gibbs energies of hydrogen bonding of amines with neat methanol was observed. It was firstly revealed that the entropy of specific interactions of amines with neat methanol can be about zero or positive. Disruption of solvent-solvent hydrogen bonds can be regarded as the most important step during dissolution of amine in methanol. It was found that the cooperative effect influences on the Gibbs energies of hydrogen bonding of amines in methanol, but in a lesser extent than in aqueous solutions. The new results show that the hydrogen bonding process in the self-associated solvents differs significantly from equimolar complexation in aprotic media. © 2012 Elsevier B.V. All rights reserved.

The properties of solutes and their reactivity in aliphatic alcohols significantly depend on the formation of hydrogen bonds. In this work, calorimetric, FTIR-spectroscopic and gas chromatographic vapor pressure studies of hydrogen bonds of weak bases in solution of aliphatic alcohols were carried out. Enthalpies of solutions at infinite dilution of ketones, nitriles and acetates in methanol and octan-1-ol were measured. Obtained from the calorimetric data, the enthalpies of specific interaction of weak bases in aliphatic alcohols unexpectedly found to be positive. IR spectra of solutions of ketones in aliphatic alcohols at infinite dilution were measured at different temperatures. Enthalpies of specific interaction in studied systems obtained from the spectroscopic data confirmed the endothermic process and are in good agreement with calorimetric results. Gibbs energies and entropies of specific interaction of weak bases in aliphatic alcohols were determined. Obtained results show, that the hydrogen bonding process of weak bases in aliphatic alcohols differs substantially from the formation of complexes 1:1 ROH⋯B (B - weak proton acceptor) in aprotic media. The complicated process of hydrogen bonding of weak bases in aliphatic alcohols apparently is controlled by the entropy factor, because these values are above zero. © 2011 Elsevier B.V. All rights reserved.

The work is devoted to the investigation of thermodynamics of specific interaction of the tertiary aliphatic and aromatic amines with associated solvents as which aliphatic alcohols were taken. Solution enthalpies of aliphatic alcohols in amines (tri-n-propylamine, 2-methylpyridine, 3-methylpyridine, N-methylimidazole) as well as amines in alcohols were measured at infinite dilution. The enthalpies of specific interaction (H-bonding) in systems studied were determined based on experimental data. The enthalpies of specific interaction of amines in aliphatic alcohols significantly lower than the enthalpies of hydrogen bonding in complexes amine-alcohol of 1:1 composition determined in base media due to the reorganization of aliphatic alcohols as solvents. The determination of solvent reorganization contribution makes possible to define the hydrogen bonding enthalpies of amines with clusters of alcohols. Obtained enthalpies of hydrogen bonding in multi-particle complexes are sensitive to the influence of cooperative effect. It was shown, that hydrogen bond cooperativity factors in multi-particle complexes of alcohols with amines are approximately equal for all alcohols when pyridines and N-methylimidazole as solutes are used. At the same time, H-bonding cooperativity factors in complexes of trialkylamines with associative species of alcohols decrease with increasing of alkyl radical length in alcohol and amine molecules. This work shows that the thermodynamic functions of specific interaction of solutes with associated solvents cannot be described using the H-bond parameters for the complexes of 1:1 composition. © 2011 Elsevier Ltd. All rights reserved.