Thermodynamic properties of three adamantanols in the ideal gas state

The enthalpies of sublimation and the saturated vapor pressure of 1-adamantanol (1-Adol), 2-adamantanol (2-Adol) and 2-methyl-2-adamantanol (2-Me-2-Adol) were measured. Thermodynamic functions of the compounds under study in the ideal gas state between 100 and 1000 K were calculated by the statistical thermodynamic methods. The sets of wave numbers of normal vibrations for adamantanols were obtained by semi empirical calculation (MINDO3 И MNDO/d). The experimental entropies for gaseous adamantanols and the calculated values were in the satisfactory agreement.     

Thermodynamic functions of lactams in the ideal gas state

Thermodynamic functions (enthalpy, entropy, free energy, and heat capacity) of azacycloalkan-2-ones with ring sizes n = 4–8 in the ideal gas state are calculated by means of quantum chemistry and statistical physics, using an anharmonic approximation in the range of 298–1500 K with allowance for all known conformers and optical isomers. Equilibrium structures and total energies of lactams are calculated using the B3LYP/6-311++G(3df, 3pd), B3LYP/aug-cc-pVQZ, and MP2/6-311++G(3df, 3pd) methods, and the anharmonic frequencies of the fundamental vibrations of all the investigated structures were found via B3LYP/6-311++G(3df, 3pd).     

Standard thermodynamic properties of nitrobenzene in the ideal gas state

The standard enthalpy of formation of gaseous nitrobenzene was calculated by the G3X nonempirical quantum-mechanical method. The value obtained (56 kJ/mol) was noticeably lower than the experimental enthalpy, which casts doubt on the accuracy of measurements. The thermodynamic functions (C° _p , S°, ?[G° ? H°(0)]/T, H° ? H°(0), Δ_f H°, and Δ_f G°) of nitrobenzene in the ideal gas state were calculated by the statistical thermodynamics method over the temperature range 150–1500 K (the molecular constants, including the structural parameters, vibrational frequencies, and internal rotation potential used in the calculations were taken from the literature or estimated by the quantum-mechanical method).     

Thermodynamic properties of some cyclohexyl esters in the condensed state

The heat capacities and the enthalpies of phase transitions of cyclohexyl esters (formate, acetate, butyrate, and valerate) in the condensed state between T =  (5 and 320) K were measured in a vacuum adiabatic calorimeter. It was found that all liquid compounds were supercooled by cooling them fromT =  300 K at a rate of (0.02 to 0.03)K · s ^− 1and formed glasses. Crystalline phases were obtained for all esters and the residual entropies of glasses at T →  0 were evaluated. The glass transition temperatures and the heat capacity jumps accompanying the glass transitions, as well as the thermodynamic parameters of fusion of crystalline phases, were determined for all the esters. The molar thermodynamic functions of the investigated compounds in the crystalline, liquid, supercooled liquid, and glassy states were obtained. The regular changes of some thermodynamic properties in the series of cyclohexyl esters are discussed.     

The standard thermodynamic functions of ethyl-, formyl-, and benzoylferrocene in the ideal gas state

The standard enthalpies of formation of gaseous ethylferrocene, formylferrocene, and benzoylferrocene were calculated at the B3LYP/6-311+G(3df,2p)//B3LYP/6-31G(d,p) level of density functional theory using the method of isodesmic reactions. The absolute entropy, heat capacity, and enthalpy were calculated for ethylferrocene and formylferrocene by statistical thermodynamics methods over the temperature range 100–1000 K. The molecular constants necessary for calculations (structural parameters, vibrational frequencies, and internal rotation potential) were estimated at the B3LYP/6-31G(d,p) level. Empirical estimates were used to check the reliability and mutual consistency of literature experimental data on the enthalpies of formation and entropies of several ferrocene derivatives. Unreliable data were revealed and more reliable estimates of their errors were obtained.     

Nonempirical studies of the molecular properties and thermodynamic functions of urea in the ideal gas state

Quantum-chemical calculations were performed for the equilibrium structure of isolated urea molecules using the 6-311++G** basis set and second-order M?ller-Plesset perturbation theory, density functional theory, and the coupled cluster method with the local inclusion of electron correlation. The results were used to perform statistical calculations of the standard thermodynamic functions of urea in the ideal gas state taking into account anharmonicity of normal vibrations. The contributions of dimerization and isomerization of urea molecules in the vapor phase were determined. The recommended values were compared with the available experimental data and the results of preceding calculations. Original Russian Text ? A.V. Kuznetsov, A.V. Stolyarov, 2009, published in Zhurnal Fizicheskoi Khimii, 2009, Vol. 83, No. 2, pp. 339–345.     

Thermodynamic properties of organic compounds

By employing calorimetric and cryometric methods, the melting total and the premelting enthalpies of stearic acid were measured and the phase diagrams of the solid-liquid equilibria stearic acid +A (whereA is an aromatic compound or a dicarboxylic acid or I₂) were determined.

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Zusammenfassung Die Gesamt-Schmelz-Enthalpie und die Vor-Schmelz-Enthalpie der Stearinsäure werden unter Anwendung kalorimetrischer und kryometrischer Methoden gemessen und die Phasendiagramme der festflüssigen Gleichgewichte von Stearinsäure+A (wobeiA eine aromatische Verbindung oder eine Dicarbonsäure oder I₂ ist) bestimmt.

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Résumé Mesure de l'enthalpie totale de fusion de l'acide stéarique, ainsi que de celle de pré-fusion, par calorimétrie et cryométrie. Etablissement des diagrammes de phases pour les équilibres solide-liquide du système acide stéarique +A;A désignant un composé aromatique ou un acide dicarboxylique ou I[in2].

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- + ( . I₂).

     

Thermodynamic properties of organic compounds

Journal of Thermal Analysis and Calorimetry - Calorimetric and cryometric methods were employed to measure the enthalpy and entropy of fusion of caprylamide and stearamide.     

Thermodynamic properties of some biphenyls

Journal of Thermal Analysis and Calorimetry - Densities (ρ), speeds of sound (u) and viscosities (η) are reported for binary mixtures of 2-methoxyaniline with carboxylic acids (ethanoic...     

Thermodynamic properties of some lanthanide chlorides

The heat capacities of the lanthanide chlorides NdCl₂, SmCl₂, EuCl₂, DyCl₂, TmCl₂, YbCl₂, DyCl₃, YbCl₃ and LuCl₃ were measured at 10–320 K with an adiabatic microcalorimeter.Standard thermodynamic properties were calculated from the experimental results.The heat capacities of these chlorides are composed of the lattice heat capacity and an additional contribution caused by the thermal population of the low-lying Stark electronic levels (Schottky anomaly). The Schottky heat capacity was estimated as the difference between the experimentalC _p values for the isostructural paramagnetic and diamagnetic chlorides. Experimental Schottky contributions were found to be in good agreement with those calculated for SmCl₂, TmCl₂ and YbCl₃ via a general model of the main-term Stark splitting of the respective ions in the orthorhombic and monoclinic crystal fields.

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Zusammenfassung Die Wärmekapazitäten von NdCl₂, SmCl₂, EuCl₂, DyCl₂, TmCl₂, DyCl₃, YbCl₃ und LuCl₃ wurden im Temperaturbereich 10–320 K mit einem adiabatischen Mikrokalorimeter gemessen. Aus den Ergebnissen wurden die thermodynamischen Standardwerte berechnet. Die Wärmekapazität dieser Chloride setzt sich zusammen aus der Gitter-Wärmekapazität und einem Beitrag, infolge der thermischen Besetzung der niedrig-liegenden Stark-Niveaus (Schottky-Anomalie). Die Schottky-Wärmekapazität wurde als Differenz zwischen experimentellenC _p -Werten isostruktureller para- und diamagnetischer Chloride geschätzt. Die experimentell gefundenen Schottky-Beiträge stimmen gut überein mit den Werten, die für SmCl₂, TmCl₂ und YbCl₃ nach einem verallgemeinerten Modell der Stark-Aufspaltung der Hauptterme der betreffenden Ionen im orthorhombischen bzw. monoklinen Kristallfeld berechnet wurden.

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10–320 , , , , , , . . , ( ). . SmCl₂, TmCl₂ YbCl₃ .

     

Thermodynamic properties in the gaseous state of certain monosubstituted benzenes

The vibrational vapour-phase frequencies and recently reported moments of inertia have been used for computing thermodynamic properties of one mole gas of both benzaldehyde and the two deuterated species of phenol (C₆H₅OD and C₆D₅OH) at 1 atmosphere pressure in the temperature range 200–1000 K for the first time. The earlier similar data for chlorobenzene and phenol have been revised. The gas imperfection correction has been applied to the calculated thermodynamic properties of all the molecules. The effect of hindered rotation in benzaldehyde and the three species of phenol has also been taken into account. The correction for isotopic mixing of ³⁵Cl and ³⁷Cl in chlorobenzene has been applied to improve upon the earlier results. Good agreement between the observed (where data is available) and computed values is obtained.     

Thermodynamic properties of some concentrated polymer solutions

Solubilities of several solvents were measured in four molten polymers by using an isobaric vapor-pressure apparatus. Solvent concentration ranged from 0.5 to 15 wt-%. The systems polyisoprene–benzene and polyisobutylene–benzene were studied at 80.0°C; polyisobutylene–cyclohexane was studied at 100.0°C; ethylene–vinyl acetate copolymer (EVA)–cyclohexane, EVA–isooctane, and poly(vinyl acetate)–isooctane were studied at 110.0°C. Of six polymer–solvent systems studied, all except poly(vinyl acetate)–isooctane appear to exhibit hysteresis in a single sorption–desorption cycle starting with dry polymer. The desorption curves of solvent activity plotted versus solvent weight fraction show an inflection point, suggesting localized adsorption of solvent molecules. Experimental data were analyzed with a theory which takes into account adsorption of solvent by polymer in addition to differences in free volumes and intermolecular forces. The theory gives a semiquantitative representation of the experimental data.     

Thermodynamic properties and conductivities of some dodecylsurfactants in water

Densities, heat capacities, enthalpies of dilution, osmotic coefficients and conductivities are reported for dodecylamine hydrochloride, dodecyldimethylammonium and dodecyltrimethylammonium chloride in water over a wide range of concentration. The last two properties were also measured for dodecyltrimethylammonium bromide. From the thermodynamic data partial molar volumes, heat capacities and relative enthalpies and nonideal free energies and entropies were derived as a function of the surfactant concentration. The cmc's and degree of counterion dissociation were also calculated from the transport properties. It is shown that the trends of volumes, enthalpies, free energies and entropies are quite regular whereas heat capacities present maxima and minima at concentrations which depend on the nature of surfactants. Corresponding changes were observed in the osmotic coefficients and specific conductivities. The thermodynamic functions of micellization were evaluated on the basis of the pseudo-phase transition model. Finally, the effects of the introduction of methyl groups in the hydrophilic moiety of the surfactant and of the nature of the counterion on the thermodynamic properties of monomers and micelles are examined.     

Thermodynamic and crystallographic properties of REPd intermetallic compounds

REPd phases have been extensively studied both by thermal, crystallographic, thermodynamic and micrographic methods. As a result of this investigation a possible sequence of structures is proposed which is correlated with the thermal and thermodynamic data.Europium is a divalent rare earth in EuPd while ytterbium in YbPd seems to be present with certain, fixed percentage of atoms in the trivalent state.     

Thermodynamic properties of organic compounds. Note III

Journal of Thermal Analysis and Calorimetry - Calorimetric and cryometric methods are employed to measure the enthalpies of fusion and prefusion of some organic acids.     

Thermodynamic molar properties of some aqueous micellar systems

Densities and ultrasonic velocities are measured then the partial molar volumes and adiabatic compressibilities are calculated at various concentrations of aqueous solutions of sodium dodecyl sulphate , sodium cholate and sodium taurcholate. These three detergents are known to form aggregates called micelles at specific concentrations. These concentrations are given the name , critical micelle concentration (cmc). Due to the nonlinear behaviour of the thermodynamic partial molar parameters with detergent's concentration no quantitative conclusions could be drawn . However, a reasonable qualitative model is put forward to explain the results.     

Magnetic properties of some aromatic compounds

The effect of hydrogen bonds on the anisotropy of the diamagnetic susceptibility of 2-amino-3-methyl-benzoic acid, 2-hydroxy-3-methylbenzoic acid and o-aminobenzoic acid has been studied. From measured values of the crystal susceptibilities and molecular orientations, the principal molecular susceptibilities have been calculated. The observed anisotropics are interpreted in the light of the hydrogen bonding of these molecules.