Recommended sublimation pressure and enthalpy of benzene

Recommended vapor pressures of solid benzene (CAS Registry Number: 71-43-2) which are consistent with thermodynamically related crystalline and ideal-gas heat capacities as well as with properties of the liquid phase at the triple point temperature (vapor pressure, enthalpy of vaporization) were established. The recommended data were developed by a multi-property simultaneous correlation of vapor pressures and related thermal data. Vapor pressures measured in this work using the static method in the temperature range from 233 K to 260 K, covering pressure range from 99 Pa to 1230 Pa, were included in the simultaneous correlation. The enthalpy of sublimation was established with uncertainty significantly lower than the previously recommended values.     

Thermodynamic properties of 4-tert-butyl-diphenyl oxide

The main thermodynamic functions (changes of the entropy, enthalpy, and Gibbs free energy) and functions of formation at T = 298.15 K of 4-tert-butyl-diphenyl oxide in condensed and ideal gas states were computed on the basis of experimental results obtained. The heat capacities of 4-tert-butyl-diphenyl oxide was measured by vacuum adiabatic calorimetry over the temperature range (8 to 371) K. The temperature, the enthalpy and the entropy of fusion were determined. The energy of combustion of the sample was determined by static-bomb combustion calorimetry. The saturation vapor pressures of the substance were measured by dynamic transpiration method over the temperature and pressure intervals (298 to 325) K and (0.05 to 1.2) Pa. The enthalpy of sublimation at T = 298.15 K was derived. The contribution of O-(2C_b) group (where C_b is the carbon atom in a benzene ring) into the absolute entropies of diphenyl oxide derivatives was assessed.     

Thermodynamic properties of tert-butylbenzene and 1,4-di-tert-butylbenzene

Heat capacities, enthalpies of phase transitions, and derived thermodynamic properties over the temperature range 5 < (T/K) < 442 were determined with adiabatic calorimetry for tert-butylbenzene (TBB) {Chemical Abstracts Service registry number (CASRN) [98-06-6]} and 1,4-di-tert-butylbenzene (DTBB) {CASRN [1012-72-2]}. A crystal to plastic crystal transition very near the triple-point temperature of DTBB was observed. New vapor pressures near the triple-point temperature are also reported for DTBB for the liquid and crystal states. These new measurements, when combined with published results, allow calculation of the thermodynamic properties for the ideal gas state for both compounds. The contribution of the tert-butyl group to the entropy of the ideal gas is determined quantitatively here for the first time based on the calorimetric results over the temperature range 298.15 < (T/K) < 600. Comparisons with literature values are shown for all measured and derived properties, including entropies for the ideal gas derived from quantum chemical calculations.     

High-temperature calorimetry of zirconia: Heat capacity and thermodynamics of the monoclinic–tetragonal phase transition

The high-temperature heat capacity of zirconia was directly measured by differential scanning calorimetry between T = (1050 and 1700) K and derived from the heat content measured by transposed temperature drop calorimetry between T = (970 and 1770) K, including the monoclinic–tetragonal (m–t) phase transition region. The enthalpy and entropy of the m–t phase transition are (5.43 ± 0.31) kJ · mol⁻¹ and (3.69 ± 0.21) J · K⁻¹ · mol⁻¹, respectively. Values of thermodynamic functions are provided from room temperature to 2000 K.     

Thermodynamic properties of the methyl esters of p-hydroxy and p-methoxy benzoic acids

The vapor pressures of crystalline and liquid phases of methyl p-hydroxybenzoate and of methyl p-methoxybenzoate were measured over the temperature ranges (338.9 to 423.7) K and (292.0 to 355.7) K respectively, using a static method based on diaphragm capacitance gauges. The vapor pressures of the crystalline phase of the former compound were also measured in the temperature range (323.1 to 345.2) K using a Knudsen mass-loss effusion technique. The results enabled the determination of the standard molar enthalpies, entropies and Gibbs free energies of sublimation and of vaporization, at T = 298.15 K, as well as phase diagram representations of the (p, T) experimental data, including the triple point. The temperatures and molar enthalpies of fusion of both compounds were determined using differential scanning calorimetry and were compared with the results indirectly derived from the vapor pressure measurements. The standard (p° = 10⁵ Pa) molar enthalpies of formation, in the crystalline phase, at T = 298.15 K, of the compounds studied were derived from their standard massic energies of combustion measured by static-bomb combustion calorimetry. From the experimental results, the standard molar enthalpies of formation, in the gaseous phase at T = 298.15 K, were calculated and compared with the values estimated by employing quantum chemical computational calculations. A good agreement between experimental and theoretical results is observed. To analyze the thermodynamic stability of the two compounds studied, the standard Gibbs free energies of formation in crystalline and gaseous phases were undertaken. The standard molar enthalpies of formation of the title compounds were also estimated from two different computational approaches using density functional theory-based B3LYP and the multilevel G3 methodologies.     

Thermodynamic properties of 9-fluorenone: Mutual validation of experimental and computational results

Measurements leading to the calculation of thermodynamic properties for 9-fluorenone (IUPAC name 9H-fluoren-9-one and Chemical Abstracts registry number [486-25-9]) in the ideal-gas state are reported. Experimental methods were adiabatic heat-capacity calorimetry, inclined-piston manometry, comparative ebulliometry, and combustion calorimetry. Critical properties were estimated. Molar entropies for the ideal-gas state were derived from the experimental studies at selected temperatures T between T = 298.15 K and T = 600 K, and independent statistical calculations were performed based on molecular geometry optimization and vibrational frequencies calculated at the B3LYP/6 − 31 + G(d,p) level of theory. Values derived with the independent methods are shown to be in excellent accord with a scaling factor of 0.975 applied to the calculated frequencies. This same scaling factor was successfully applied in the analysis of results for other polycyclic molecules, as described in recent articles by this research group. All experimental results are compared with property values reported in the literature. Thermodynamic consistency between properties is used to show that several studies in the literature are erroneous.     

The heat capacities and thermodynamic functions of some derivatives of ferrocene

The heat capacities of benzoylferrocene (BOF), C₅H₅FeC₅H₄COC₆H₅, and benzylferrocene (BF), C₅H₅FeC₅H₄CH₂C₆H₅, have been measured by the low-temperature adiabatic calorimetry in the temperature range from 6 K to 372 K. The purity benzylferrocene and thermodynamic properties – the triple point temperature and the enthalpy of fusion have been obtained. The ideal gas thermodynamic functions (changes of the entropy, enthalpy, and Gibbs free energy) of BOF and BF were derived at T = 298.15 K using the heat capacities and previously determined data on the saturation vapours pressures and the enthalpies of sublimation. The ideal gas enthalpy of formation and absolute entropy of BOF at T = 298.15 K have been obtained from quantum chemical calculations, where as the thermodynamic properties of BF have been estimated by empirical method of group equations. A good agreement between experimental and theoretical values provides an additional check of the reliability of the experimental data.     

Thermodynamic properties of 1,2-dihydronaphthalene: Glassy crystals and missing entropy

Measurements leading to the calculation of the standard thermodynamic properties for gaseous 1,2-dihydronaphthalene (Chemical Abstracts registry number [447-53-0]) are reported. Experimental methods include oxygen combustion-bomb calorimetry, adiabatic heat-capacity calorimetry, vibrating-tube densitometry, comparative ebulliometry, and inclined-piston gauge manometry. 1,2-Dihydronaphthalene decomposed significantly when heated to temperatures above T = 480 K. Consequently, the critical temperature, critical pressure, and critical density were estimated. Standard molar entropies, standard molar enthalpies, and standard molar Gibbs free energies of formation were derived at selected temperatures between T = 250 K and 500 K. The standard state is defined as the ideal gas at the pressure p = p^° = 101.325 kPa. Standard entropies are compared with those calculated statistically on the basis of assigned vibrational spectra from the literature for the vapor phase. A large and near constant difference between the entropies calculated statistically and those determined calorimetrically was observed over the entire temperature range studied. Two glass-like features are observed in the heat capacity against temperature curve for the solid state, indicating that the crystals are disordered. A quantitative accounting for the entropy discrepancy is proposed based on possible molecular orientations of 1,2-dihydronaphthalene. Results are compared with experimental values reported in the literature.     

Thermodynamic properties of 1-alkyl-3-methylimidazolium bromide ionic liquids

Heat capacities and enthalpies of phase transitions for a series of 1-alkyl-3-methylimidazolium bromide ionic liquids have been measured by adiabatic calorimetry. Thermodynamic properties of the compounds were calculated in the temperature range of (5 to 370) K. Water was found to have an additive contribution to the heat capacities of [C₄mim]Br in the liquid state above T_fus and in the solid state below 160 K at w(H₂O) ⩽ 5 · 10⁻³.     

The low-temperature heat capacity and ideal gas thermodynamic properties of isobutyl tert-butyl ether

The heat capacities of isobutyl tert-butyl ether in crystalline, liquid, supercooled liquid, and glassy states were measured by vacuum adiabatic calorimetry over the temperature range from (7.68 to 353.42) K. The purity of the substance, the glass-transition temperature, the triple point and fusion temperatures, and the enthalpy and entropy of fusion were determined. Based on the experimental data, the thermodynamic functions (absolute entropy and changes of the enthalpy and Gibbs free energy) were calculated for the solid and liquid states over the temperature range studied and for the ideal gas state at T = 298.15 K. The ideal gas heat capacity and other thermodynamic functions in wide temperature range were calculated by statistical thermodynamics method using molecular parameters determined from density-functional theory. Empirical correction for coupling of rotating groups was used to calculate the internal rotational contributions to thermodynamic functions. This correction was found by fitting to the calorimetric entropy values.     

Thermodynamic properties of three-ring aza-aromatics. 1. Experimental results for phenazine and acridine,and mutual validation of experiments and computational methods

Measurements leading to the calculation of thermodynamic properties for phenazine (Chemical Abstracts registry number [92-82-0]) in the ideal-gas state are reported. Experimental methods included adiabatic heat-capacity calorimetry, inclined-piston manometry, and combustion calorimetry. Thermodynamic properties for acridine (Chemical Abstracts registry number [260-94-6]) were reported previously and included those measured with adiabatic heat-capacity calorimetry, comparative ebulliometry, inclined-piston manometry, and combustion calorimetry. New measurement results for acridine reported here are densities determined with a vibrating-tube densimeter and heat capacities for the liquid phase at saturation pressure determined with a differential-scanning calorimeter (d.s.c.). All critical properties were estimated. Molar entropies for the ideal-gas state were derived for both compounds at selected temperatures. Independent calculations of entropies for the ideal-gas state were performed at the B3LYP/6-31+G(d, p) model chemistry for phenazine and acridine. These are shown to be in excellent accord with the calorimetric results. All results are compared with experimental property values reported in the literature.     

(Solid + liquid) phase equilibria and heat capacity of (diphenyl ether + biphenyl) mixtures used as thermal energy storage materials

The (solid + liquid) phase equilibrium for eight {x diphenyl ether + (1 − x) biphenyl} binary mixtures, including the eutectic mixture were studied by using a differential scanning calorimetry (DSC) technique. A good agreement was found between previous literature and experimental values here presented for the melting point and enthalpy of fusion of pure compounds. The well-known equations for Wilson and the non-random two-liquid (NRTL) were used to correlate experimental solid liquid phase equilibrium data. Moreover, the predictive mixture model UNIFAC has been employed to describe the phase diagram. With the aim to check this equipment to measure heat capacities in the quasi-isothermal Temperature-Modulated Differential Scanning Calorimetry method (TMDSC), four fluids of well-known heat capacity such as toluene, n-decane, cyclohexane and water were also studied in the liquid phase at temperatures ranging from (273.15 to 373.15) K. A good agreement with literature values was found for those fluids of pure diphenyl ether and biphenyl. Additionally, the specific isobaric heat capacities of diphenyl ether and biphenyl binary mixtures in the liquid phase up to T = 373.15 K were measured.     

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.     

Experimental and theoretical study of thermodynamic properties of levoglucosan

The heat capacity of levoglucosan was measured over the temperature range (5 to 370) K by adiabatic calorimetry. The temperatures and enthalpies of a solid-phase transition and fusion for the compound were found by DSC. The obtained results allowed us to calculate thermodynamic properties of crystalline levoglucosan in the temperature range (0 to 384) K. The enthalpy of sublimation for the low-temperature crystal phase was found from the temperature-dependent saturated vapor pressures determined by the Knudsen effusion method. The thermodynamic properties of gaseous levoglucosan were calculated by methods of statistical thermodynamics using the molecular parameters from quantum chemical calculations. The enthalpy of formation of the crystalline compound was found from the experiments in a combustion calorimeter. The gas-phase enthalpy of formation was also obtained at the G4 level of theory. The thermodynamic analysis of equilibria of levoglucosan formation from cellulose, starch, and glucose was conducted.     

Low temperature heat capacity Study of Fe(PO3)3 and Fe2P2O7

The heat capacities of two iron phosphates, Fe(PO₃)₃ and Fe₂P₂O₇, have been measured over the temperature range from (2 to 300) K using the heat capacity option of a Quantum Design Physical Property Measurement System (PPMS). A phase transition related to magnetic ordering has been found in the heat capacity at T = 8.76 K for Fe(PO₃)₃ and T = 18.96 K for Fe₂P₂O₇, which are comparable with literature values from magnetic measurements. By fitting the experimental heat capacity values, the thermodynamic functions, magnetic heat capacities, and magnetic entropies have been determined. Additionally, theoretical fits at low temperatures suggest that Fe₂P₂O₇ has an anisotropic antiferromagnetic contribution to the heat capacity and a large linear term likely caused by oxygen vacancies. Further data fitting in a series over widened temperature regions found that this linear term exists only below 15 K and disappears gradually from (15 to 17) K.     

Thermodynamic study of (anthracene + phenanthrene) solid state mixtures

Polycyclic aromatic hydrocarbons (PAH) are common components of many materials, such as petroleum and various types of tars. They are generally present in mixtures, occurring both naturally and as byproducts of fuel processing operations. It is important to understand the thermodynamic properties of such mixtures in order to understand better and predict their behavior (i.e., fate and transport) in the environment and in industrial operations. To characterize better the thermodynamic behavior of PAH mixtures, the phase behavior of a binary (anthracene + phenanthrene) system was studied by differential scanning calorimetry, X-ray diffraction, and the Knudsen effusion technique. Mixtures of (anthracene + phenanthrene) exhibit non-ideal mixture behavior. They form a lower-melting, phenanthrene-rich phase with an initial melting temperature of 372 K (identical to the melting temperature of pure phenanthrene) and a vapor pressure of roughly lnP/Pa = −2.38. The phenanthrene-rich phase coexists with an anthracene-rich phase when the mole fraction of phenanthrene (x_P) in the mixture is less than or equal to 0.80. Mixtures initially at x_P = 0.90 consist entirely of the phenanthrene-rich phase and sublime at nearly constant vapor pressure and composition, consistent with azeotrope-like behavior. Quasi-azeotropy was also observed for very high-content anthracene mixtures (2.5 < x_P < 5) indicating that anthracene may accommodate very low levels of phenanthrene in its crystal structure.     

Deuterium isotope effect on molar heat capacities and apparent molar heat capacities in dilute aqueous solutions: A multi-channel heat-flow microcalorimeter study

The molar heat capacities of chloroform, dichloromethane, methanol, acetonitrile, acetone, dimethyl sulfoxide, benzene, dimethylformamide, toluene, and cyclohexane, as well as their deuterated isotopologues, were measured using a multi-channel heat conduction TAM (Thermal Activity Monitor) III microcalorimeter. In addition, the apparent molar heat capacities of some of the associated dilute aqueous solutions (0.0039 < solute mole fraction, x_i < 0.0210) were also measured. A temperature drop method from (298.15 to 297.15) K at 0.1 MPa was employed. The corresponding heat capacities were determined from the integration of the measured heat flow. The heat capacity results are shown to be in good to very good agreement with the available literature values. In addition, good correlations were obtained for the effect of isotopic substitution on both molar heat capacity and apparent molar heat capacity in aqueous solutions. These correlations should be useful in the prediction of the molar heat capacities or the apparent molar heat capacities of other deuterated compounds. Since these measurements were conducted with ampoules, the effects of heat of condensation and/or vapor space on the accuracy of the heat capacity determinations are discussed. The overall results from this study demonstrate the utility of a multi-channel heat conduction microcalorimeter in obtaining good reproducibility and good accuracy for molar heat capacities as well as apparent molar heat capacities from simultaneous samples.     

Thermodynamic study of phase transitions in methyl esters of ortho- meta- and para-aminobenzoic acids

A static method based on capacitance gauges was used to measure the vapor pressures of the condensed phases of the methyl esters of the three aminobenzoic acids. For methyl o-aminobenzoate the vapor pressures of the liquid phase were measured in the range (285.4 to 369.5) K. For the meta and para isomers vapor pressures of both crystalline and liquid phases were measured in the ranges (308.9 to 376.6) K, and (332.9 to 428.0) K, respectively. Vapor pressures of the latter compound were also measured using the Knudsen effusion method in the temperature range (319.1 to 341.2) K.From the dependence of the vapor pressures on the temperature, the standard molar enthalpies and entropies of sublimation and of vaporization were derived. Differential scanning calorimetry was used to measure the temperatures and molar enthalpies of fusion of the three isomers. The results enabled the estimation of the enthalpy of the intermolecular (N−H^…O) hydrogen bond in the crystalline methyl p-aminobenzoate. A correlation relating the temperature of fusion and the enthalpy and Gibbs energy of sublimation of benzene, methyl benzoates and benzoic acids was derived.     

Speed of sound,ideal-gas heat capacity at constant pressure,and second virial coefficients of HFC-227ea

The speed of sound of the gaseous 1,1,1,2,3,3,3-heptafluoropropane (HFC-227ea) was measured for temperatures from 273 to 333 K and pressures from 26 to 315 kPa with a cylindrical, variable-path acoustic interferometer operating at 156.252 kHz. The uncertainty of the speed of sound was less than ±0.05%. The ideal-gas heat capacity at constant pressure and the second acoustic virial coefficients were determined over the temperature range from the speed of sound measurements. The uncertainty of the ideal-gas heat capacity at constant pressure was estimated to be less than ±0.5%. The ideal-gas heat capacity at constant pressure results and second virial coefficients calculated from the present speed of sound measurements were compared with the available data.     

Partial molar heat capacities and volumes of transfer of some saccharides from water to aqueous sodium chloride solutions at T=298.15 K

Partial molar heat capacities (C^o_p,2,m) and volumes (V^o_2,m) of seven monosaccharides, namely, d(−)-ribose, d(−)-arabinose, d(+)-xylose, d(+)-glucose, d(+)-mannose, d(+)-galactose, and d(−)-fructose; five disaccharides, namely, sucrose, d(+)-cellobiose, d(+)-maltose monohydrate, d(+)-lactose monohydrate, d(+)-trehalose dihydrate, and one trisaccharide, d(+)-raffinose pentahydrate, have been determined in NaCl(aq), m = (1.0, 2.0, and 3.0) mol·kg⁻¹ at T=298.15 K from volumic heat capacity and density measurements employing a Picker flow microcalorimeter and a vibrating-tube densimeter, respectively. These data were combined with the earlier reported C^o_p,2,m and V^o_2,m values in water to calculate the corresponding partial molar properties of transfer (Δ_trC^o_p,2,m and Δ_trV^o_2,m) from water to aqueous sodium chloride solutions at infinite dilution. These transfer parameters are positive, and the values increase with the concentration of sodium chloride for all the saccharides. Transfer parameters have been discussed in terms of solute-cosolute interactions on the basis of a cosphere overlap model. Pair and higher-order interaction coefficients have also been calculated from transfer parameters.