The thermodynamic properties of delta-lactones

The enthalpies of formation of δ-hexanolactone and δ-nonanolactone were determined by combustion calorimetry. Conformational analysis and quantum-chemical calculations of equilibrium structures, fundamental vibrations, moments of inertia, and total energies were performed for δ-pentanolactone (I), δ-hexanolactone (II), and δ-nonanolactone (III) by the B3LYP/6-311G(d,p), B3LYP/6-311++G(d,p), and G3MP2 methods. The experimental IR spectra and calculated vibrational frequencies were used to suggest the assignment of vibrational frequencies of stable conformations. The thermodynamic properties of I–III in the ideal gas state were determined over the temperature range 0–1500 K. A thermodynamic analysis of mutual isomerization in the gas and liquid phases over the temperature range 298.15–900 K and liquid-phase polymerization of γ- and δ-pentanolactones and 4-pentenoic acid over the temperature range 298.15–500 K was performed.     

The thermodynamic properties of polytetrafluoroethylene

Polytetrafluoroethylenes of different crystallinity were analyzed between 220 and 700 K by differential scanning calorimetry. A new computer coupling of the standard DSC is described. The measured heat capacity data were combined with all literature data into a recommended set of thermodynamic properties for the crystalline polymer and a preliminary set for the amorphous polymer (heat capacity, enthalpy, entropy, and Gibbs energy; range 0–700 K). The crystal heat capacities have been linked to the vibrational spectrum with a θ₃ of 54 K, and θ₁ of 250 K, and a full set of group vibrations. C_v to C_p conversion was possible with a Nernst–Lindemann constant of A = 1.6 × 10^?3 mol K/J. The glass transition was identified as a broad transition between 160 and 240 K with a ΔC_p of 9.4 J/K mol. The room-temperature transitions at 292 and 303 K have a combined heat of transition of 850 J/mol and an entropy of transition of 2.90 J/K mol. The equilibrium melting temperature is 605 K with transition enthalpy and entropy of 4.10 kj/mol and 6.78 J/K mol, respectively. The high-temperature crystal from is shown to be a condis crystal (conformationally disordered), and for the samples discussed, the crystallinity model holds.     

The thermodynamic properties of Al-Ce melts

Thermodynamic modeling of Al-Ce melts was performed at a total pressure p = 10⁵ Pa in an argon atmosphere over the temperature and concentration ranges 1773–2373 K and 0 ≤ x _Ce ≤ 1, respectively, corresponding to the liquid-phase region of the phase diagram of the system. The concentration and temperature dependences of the thermodynamic characteristics of the melts and the contents of melt components and gas phase components over the melts were calculated, the temperatures, enthalpies, and entropies of the liquid-gas transition were determined, and the phase diagram of the liquid-liquid + gas-gas transition was obtained.     

The thermodynamic properties of natural margarite

Thermal, IR spectroscopic, and thermochemical studies of natural brittle mica, margarite Ca_1.00Na_0.10Mg_0.02Al_3.89Fe_0.01³⁺Si_2.03Ti_0.01O₁₀(OH)_1.74F_0.26, were performed. The enthalpy of formation of natural margarite from the elements (−6269 ± 12 kJ/mol) was determined by melt solution calorimetry on a high-temperature heat-conducting Calvet microcalorimeter (Setaram, France). Enthalpy growth over the temperature range 298.15–973 K was determined by the drop method. Equations for the temperature dependences of the enthalpy and heat capacity were obtained, H°(T)−H°(298.15 K), J/mol = 435.21T + 36.46 × 10⁻³ T ² + 109.91 × 10⁵/T − 169863 and C° _p , J/(mol K) = 435.21 + 72.92 × 10⁻³ T − 109.91 × 10⁵/T ². The experimental data were used to estimate the thermodynamic properties of margarite of the theoretical composition, CaAl₂[Al₂Si₂O₁₀](OH)₂.     

The thermodynamic properties of magnesium uranoborate

The standard enthalpy of formation of crystalline Mg(BUO₅)₂ at 298.15 K (?4347.5 ± 8.0 kJ/mol) was determined by reaction calorimetry. The heat capacity of magnesium uranoborate was studied by adiabatic vacuum calorimetry over the temperature range 8–330 K. The thermodynamic functions of the compound were calculated. The standard entropy and Gibbs energy of formation at 298.15 K were found to be ?903.0 ± 2.1 J/(mol K) and ?4078.5 ± 9.0 kJ/mol, respectively.     

The thermodynamic properties of calcium uranoborate

The standard enthalpy of formation of crystalline Ca(BUO₅)₂ at 298.15 K was determined by reaction calorimetry (?4491.0 ± 3.5 kJ/mol). The heat capacity of the substance was measured over the temperature range 7–304 K by adiabatic vacuum calorimetry, and its thermodynamic functions were calculated. The standard entropy and the Gibbs function of formation at 298.15 K were found to be ?887.1 ± 2.1 J/(mol K) and-4226.5 ± 4.0 kJ/mol, respectively. The standard thermodynamic functions of calcium uranoborate synthesis reactions were calculated and analyzed.     

The thermodynamic properties of S-lactic acid

The enthalpies of combustion and formation of S-lactic acid at 298.15 K, Δ_c H _m^o(cr.) = −1337.9 ± 0.8 and Δ_f H _m^o(cr.) = −700.1 ± 0.9 kJ/mol, were determined by calorimetry. The temperature dependence of acid vapor pressure was studied by the transpiration method, and the enthalpy of its vaporization was obtained, Δ_vap H ^o(298.15 K) = 69.1 ± 1.0 kJ/mol. The temperature and enthalpy of fusion, T _m (330.4 K) and Δ_m H ^o(298.15 K) = 14.7 ± 0.2 kJ/mol, were determined by differential scanning calorimetry. The enthalpy of formation of the acid in the gas phase was obtained. Ab initio methods were used to perform a conformational analysis of the acid, calculate fundamental vibration frequencies, moments of inertia, and total and relative energies of the stablest conformers. Thermodynamic properties were calculated in the ideal gas state over the temperature range 0–1500 K. A thermodynamic analysis of mutual transformation processes (the formation of SS- and RS(meso)-lactides from S-lactic acid and the racemization of these lactides) and the formation of poly-(RS)-lactide from S-lactic acid and SS- and RS(meso)-lactides was performed.     

The thermodynamic properties of uranyl metaborate

The standard enthalpy of formation of crystalline UO₂(BO₂)₂ at 298.15 K was determined by reaction calorimetry (?2542.5 ± 3.5 kJ/mol). The heat capacity of this compound was measured over the temperature range 6–302 K by adiabatic vacuum calorimetry. The thermodynamic functions were calculated, including the standard entropy (502.8 ± 2.1 J/(mol K)) and Gibbs function of formation (?2392.5 ± 4.0 kJ/mol) at 298.15 K. The standard thermodynamic functions of reactions with the participation of uranyl metaborate were determined and analyzed.     

The thermodynamic properties of star-shaped fullerene-containing poly-N-vinylpyrrolidone

The temperature dependence of the heat capacity of star-shaped fullerene-containing poly-N-vinylpyrrolidone was studied over the temperature range 6–390 K by precision adiabatic vacuum and dynamic scanning calorimetry. The temperature intervals and thermodynamic characteristics of phase transitions were determined. The low-temperature dependence of the heat capacity of the substance was analyzed according to the Debye theory of the heat capacity of solids and its multifractal generalization. The data obtained were used to calculate the standard thermodynamic functions C _p ^o (T),H ^o(T)-H ^o(0), S ^o(T), and G ^o(T)-H ^o(0) of fullerene-containing poly-N-vinylpyrrolidone from T → 0 to 390 K. The standard entropy of formation of the polymer from simple substances and the entropy of its synthesis from poly-N-vinylpyrrolidone and fullerite C₆₀ at 298.15 K were calculated. The thermodynamic characteristics of fullerene-containing poly-N-vinylpyrrolidone are compared with those of the polymer-analogue without C₆₀.     

The thermodynamic properties of magnesium uranoborate tetrahydrate

The standard enthalpy of formation of crystalline Mg(BUO₅)₂ · 4H₂O at 298.15 K (?5563 ± 10 kJ/mol) was determined by reaction calorimetry. The heat capacity of the compound was studied over the temperature range 8–340 K by adiabatic vacuum calorimetry, and its thermodynamic functions were calculated. The standard entropy and Gibbs function of formation at 298.15 K (?1692.2 ± 3.4 J/(mol K) and ?5059 ± 11 kJ/mol, respectively) were determined.     

The thermodynamic properties of Al-Si system melts

The thermochemical properties of Al-Si system melts were determined by an improved isoperibolic calorimetry method. The data obtained correlated with the reliable partial and integral enthalpies of mixing reported in the literature. The method developed was used to model the thermodynamic properties of melts with the use of the liquidus coordinates of the phase diagram of the Al-Si system. The modeled and experimental results were in close agreement with each other.     

The thermodynamic properties of 4-pentenoic acid

The enthalpy of formation of liquid 4-pentenoic acid was determined by combustion calorimetry. The vapor pressure and enthalpy of vaporization of the compound were measured by the transfer method over the temperature range 289–324 K. Conformational analysis was performed. The equilibrium structure, fundamental vibrations, moments of inertia, and total energy of the stablest acid conformers were calculated by the B3LYP/6-311G(d, p) and G3MP2 quantum-chemical methods. The experimental IR spectrum and calculated vibrational frequencies were used to assign IR bands. The thermodynamic properties of monomeric 4-pentenoic acid in the ideal gas state were calculated over the temperature range 0–1500 K. Additive and quantum-chemical methods were used to estimate the Δ_f H°(g) and Δ_vap H° values. Close agreement between the calculation results and experimental data was obtained. It was shown that additive and quantum-chemical methods could be used for estimating the enthalpies of formation and vaporization of nonconjugated alkenoic acids.     

The thermodynamic properties of DL- and L-lactides

The enthalpies of formation of DL-lactide and L-lactide, cyclic esters of lactic acid, were determined by combustion calorimetry. The transfer method was used to measure their vapor pressures and obtain the enthalpies of sublimation. A conformational analysis of lactides was performed, and the most stable conformations were determined. The equilibrium structures of lactides, sets of fundamental vibrations, moments of inertia, and total energies of the most stable conformers were calculated quantum-chemically at the B3LYP/6-311++G(3df,3pd) level. The G3MP2 composite method was used to estimate the enthalpies of formation of lactides in the gas phase. The thermodynamic properties of lactides in the ideal gas state were calculated over the temperature range 100–1500 K.     

The thermodynamic properties of 1,4-dioxane-2,6-dione

The enthalpies of combustion and formation of 1,4-dioxane-2,6-dione were determined by combustion calorimetry. The transpiration method was used to obtain the temperature dependence of compound vapor pressures and the enthalpies of sublimation and vaporization. Differential scanning calorimetry was used to measure the enthalpy of fusion. Quantum-chemical calculations of the geometric, vibrational, and energy characteristics of the compound were performed, and the enthalpy of formation of the compound in the gas phase was estimated. Statistical thermodynamics methods were used to determine the thermodynamic properties of the compound in the ideal gas state over the temperature range 0–1500 K. Strain energies of some representatives of six-membered cyclic compounds were estimated.     

The thermodynamic properties of four triphenylsilane acetylene peroxides

The enthalpies of formation of four acetylene triphenylsilane peroxides were determined in the condensed and gaseous states. Three silicon-containing fragment increments for the Benson additive scheme and the enthalpies of formation of three radicals formed in the dissociation of the compounds at the O-O bond were calculated.     

The thermodynamic properties of Ba2SrUO6

The standard enthalpy of formation of crystalline Ba₂SrUO₆ at 298.15 K was determined by reaction calorimetry (-2940.0 ± 8.5 kJ/mol). The heat capacity of the compound was measured over the temperature range 8-330 K by adiabatic vacuum calorimetry. The thermodynamic functions of Ba₂SrUO₆ were calculated. The standard entropy (-558.6 ± 2.1 J/(mol K)) and Gibbs function of formation at 298.15 K (-2773.5 ± 9.0 kJ/mol) were determined.     

The thermodynamic properties of yttrium and dysprosium manganites

The temperature dependences of the Gibbs energies of formation of RMnO₃ (R = Y, Dy) from the coexisting phases R₂O₃ + 2RMn₂O₅ = 4RMnO₃ + 0.5O₂ were determined by the electromotive force (EMF) method with a fluorine ion conducting electrolyte. The temperature dependences of log P (O₂) for the dissociation reactions RMn₂O₅ ? RMnO₃ + (1/3)Mn₃O₄ + (1/3)O₂ and Mn₂O₃ ? (2/3)Mn₃O₄ + (1/6)O₂ were obtained by jointly applying the methods of heterogeneous equilibria and EMF with an oxygen ion conducting electrolyte. The results were used to calculate the standard thermodynamic functions of formation of yttrium and dysprosium manganites from simple oxides.     

Excess differential thermodynamic properties

A strategy is described for the systematic generation of a complete set of partial derivatives of the four energy functions from a basis set of five measured properties: V_m, S_m, C_p,m (δV_m/δT)_p and either (δV_m/δp)_T or (δV_m/δp)_s. The same set of equations applies to both pure substances and either real or ideal mixtures.

Examples are given of some excess differential properties of binary mixtures which exhibit unusual sensitivity to changes in composition.