The thermodynamic characteristics of 15-pentadecanolide and 16-hexadecanolide

Combustion calorimetry was used to determine the enthalpies of formation of 15-pentadecanolide (I) and 16-hexadecanolide (II). The temperature dependences of vapor pressure of lactones and the enthalpies of vaporization were determined by the transpiration method. Differential scanning calorimetry measurements were performed to find the temperatures and enthalpies of fusion of lactones. Conformational analysis and quantum-chemical calculations of the structural, vibrational, and energy characteristics of stable conformers of I were performed. The molecular and spectral data were used to calculate the thermodynamic properties of I in the ideal gas state. An explanation was suggested of the special features of changes in the enthalpies of vaporization in the series of unsubstituted lactones as the size of their rings increased.     

The thermodynamic properties of alkylated γ-lactones

The enthalpies of formation of γ-pentanolactone (I), γ-hexanolactone (II), and γ-nonanolactone (III) were determined by combustion calorimetry. The enthalpies of vaporization of these lactones were measured by the transfer method. Conformational analysis was performed and equilibrium structures, sets of fundamental vibrations, moments of inertia, and total energies of the stablest conformers of I, II, and III were calculated by the B3LYP/6-311G(d,p), G3MP2, and CBS-QB3 methods. The experimental IR spectra and calculated vibrational frequencies were used to obtain sets of fundamental vibrations of the stablest conformations. The thermodynamic properties of I–III in the ideal gas state were determined over the temperature range 0–1500 K. Additive and quantum-chemical methods were applied to estimate the Δ_f H ^o(g) values of a number of γ-lactones. Composite quantum-chemical methods were used to obtain the energies of monomethyl γ-butyrolactones and estimate their relative stability depending on the position of the methyl substituent in the ring.     

Thermodynamical properties of ε-caprolactone

The values of the combustion and enthalpies of formation for ε-caprolactone were determined by means of combustion calorimetry. The vapor pressures of lactone were measured in the range of 283–353 K, and the value of its enthalpy of vaporization was estimated by the transpiration method. Conformational analysis and calculations of the equilibrium structures, inertia moments, and sets of fundamental vibrations was performed by the B3LYP/6-311++G(3 df, 3 pd) quantum-chemical method. The total energies of the most stable lactone conformers were found and Δ_fH(g) was estimated using the composite G3MP2 method. The set of fundamental vibrations for the most stable conformers of the compound was developed on the basis of the available experimental IR spectra and calculated vibration frequencies. The values of the thermodynamic properties of ε-caprolactone were determined in the ideal ga s state in the range of 0—1500 K. A set of reliable and interconsistent thermodynamic parameters for ε-caprolactone was created. Thermodynamic analysis for liquid-phase polymerization of s-caprolactone in the temperature range of 220—500 K was carried out.     

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.     

Thermochemistry of complex salts of transition metal perchlorates with tetrazole ligands

The combined use of combustion and solution calorimetry was proposed as a method for determining the standard enthalpy of formation of the complex salts of transition metals, viz., cobalt(II), nickel(II), and zinc, with the organic ligand (5-aminotetrazol-1-yl)acethydrazide. The enthalpies of solution in water and in a 0.1 M solution of hydrochloric acid were measured for the complex salts and ligand. The enthalpy of combustion of the ligand was determined by the combustion calorimetry method, and its standard enthalpy of formation was calculated. The thermochemical cycle was developed for determining the standard enthalpy of formation of the complex salts. The reliable values of the enthalpies of formation of the salts in the standard states were obtained, and the enthalpies of formation of the earlier unknown complex ions were determined.     

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.     

Synthesis and solid state structures of two new copper(II) complexes of Schiff bases derived from furfuryl and tetrahydrofurfurylamine

Two Schiff base copper(II) complexes, bis(N-furfurylsalicylaldiminato)copper(II) (I) and bis(N-tetrahydrofurfurylsalicylaldiminato)copper(II) (II), were synthesized and their solid state structures were determined by X-ray crystallography. Complex I has a square planar geometry. In contrast, complex II displays a distorted square planar geometry. Thus, the geometry around copper in the solid state structures of I and II is determined by a combination of steric and electronic effects, as well as by crystal packing forces.     

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 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 Fe(II) complexes with 1,2,4-triazoles

The temperature dependences of the heat capacities at 106–330 K of the monoligand Fe(NH₂trz)₃I₂ (I) and mixed-ligand Fe(Htrz)_0.3(NH₂trz)_2.7SiF₆ · H₂O (II) complexes (Htrz is 1,2,4-triazole, and NH₂trz is 4-amino-1,2,4-triazole) were studied by adiabatic vacuum calorimetry. The ¹A₁ ⇔ ⁵T₂ spin transition was observed in these compounds. The thermodynamic parameters of phase transitions in I and II were determined.     

Thermodynamic functions of lactones in the gaseous state

The temperature dependences of the vapor pressures of oxacyclobutan-2-one and oxacyclopentan-2-one were measured by the transpiration method. The entropies of gaseous oxacycloalkan-2-ones (lactones) were determined based on the experimental values of entropy in the condensed state, vapor pressure, and enthalpy of vaporization. Thermodynamic functions of lactones with a ring size of n = 4—8 (number of atoms in the ring) were determined by quantum chemistry and statistical physics methods in the ideal gas approximation taking into account the molar fractions of all conformers and optical isomers in the temperature range from 298.15 to 1500 K. The enthalpies of ring strain were calculated based on the enthalpies of formation.     

Thermodynamic properties of lanthanum molybdates

The enthalpy of solution of LаОНMoO₄ and Cs₂MoO₄ in aqueous HCl at 298 К has been determined by solution calorimetry, and the standard enthalpy of formation of lanthanum hydroxomolybdate has been calculated. The enthalpies of solution of NaLa(MoO₄)₂ and Na₅Lа(MoO₄)₄ in molybdate melt at 973 K have been determined by high-temperature melt solution microcalorimetry, and the high-temperature enthalpies of the double molybdates in the 298–1000 K range have been measured by the mixing method. The standard enthalpies of formation of the double molybdates have been calculated using data available from the literature. The low-temperature heat capacity of NaLa(MoO₄)₂ in the 60–300 K range has been measured on an adiabatic vacuum calorimeter. The basic thermodynamic properties of NaLa(MoO₄)₂, Na₅Lа(MoO₄)₄, and LаОНMoO₄ have been calculated.     

A calorimetric study of germanium dibromide

The temperature dependence of the heat capacity of germanium dibromide was studied over the temperature range 8.3–314 K by adiabatic calorimetry. The enthalpy of formation of solid germanium dibromide was determined by solution calorimetry. Scanning calorimetry was used to obtain the thermodynamic characteristics of fusion of GeBr₂. The thermodynamic characteristics of the Ge-Br system studied by us earlier were used to consistently calculate the consistent standard enthalpies of formation and absolute entropies of germanium bromides in the solid, liquid, and gaseous states.     

Thermochemistry of complex salts of transition metal perchlorates with tetrazole ligands

Standard enthalpies of formation of transition metal (cobalt, nickel, and zinc) complex salts with an organic ligand 5-aminotetrazol-2-ylacetohydrazide (ATH-2) were obtained by combustion and solution calorimetry. The enthalpy of combustion of the ligand was determined using combustion calorimetry and the standard enthalpy of formation of the ligand was calculated. For calculations by reaction calorimetry, a thermochemical cycle was developed that allows determination of the standard enthalpy of formation of complex salts. The enthalpies of solution of the ligand and transition metal complex salts in water and in 0.1 M hydrochloric acid were determined. The data obtained allow calculations of the enthalpies of salts formation and the enthalpies of three new complex ions. The enthalpies of position isomerization in different compounds were 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.     

A Promising Thermodynamic Study of Hole Transport Materials to Develop Solar Cells: 1,3-Bis(N-carbazolyl)benzene and 1,4-Bis(diphenylamino)benzene

The thermochemical study of the 1,3-bis(N-carbazolyl)benzene (NCB) and 1,4-bis(diphenylamino)benzene (DAB) involved the combination of combustion calorimetric (CC) and thermogravimetric techniques. The molar heat capacities over the temperature range of (274.15 to 332.15) K, as well as the melting temperatures and enthalpies of fusion were measured for both compounds by differential scanning calorimetry (DSC). The standard molar enthalpies of formation in the crystalline phase were calculated from the values of combustion energy, which in turn were measured using a semi-micro combustion calorimeter. From the thermogravimetric analysis (TGA), the rate of mass loss as a function of the temperature was measured, which was then correlated with Langmuir’s equation to derive the vaporization enthalpies for both compounds. From the combination of experimental thermodynamic parameters, it was possible to derive the enthalpy of formation in the gaseous state of each of the title compounds. This parameter was also estimated from computational studies using the G3MP2B3 composite method. To prove the identity of the compounds, the ¹H and ¹³C spectra were determined by nuclear magnetic resonance (NMR), and the Raman spectra of the study compounds of this work were obtained.     

Investigation of copper(II) complexation by glycylglycine using isothermal titration calorimetry

Isothermal titration calorimetry (ITC) and potentiometric titration methods have been used to study the process of proton transfer in the copper(II) ion-glycylglycine reaction. The stoichiometry, conditional stability constants, and thermodynamic parameters (ΔG, ΔH, and ΔS) for the complexation reaction were determined using the ITC method. The measurements were carried out at 298.15 K in solutions with a pH of 6 and the ionic strength maintained with 100 mM NaClO₄. Carrying out the measurements in buffer solutions of equal pH but different enthalpies of ionization of its components (Mes, Pipes, Cacodylate) enabled determination of the enthalpy of complex formation, independent of the enthalpy of buffer ionization. The number of protons released by glycylglycine on account of complexation of the copper(II) ions was determined from calorimetric and potentiometric measurements.     

Experimental and computational study of the thermodynamic properties of 2-nitrofluorene and 2-aminofluorene

This report presents a comprehensive experimental and computational study of the thermodynamic properties of two fluorene derivatives: 2-aminofluorene and 2-nitrofluorene. The standard (p° = 0.1 MPa) molar enthalpies of formation in the crystalline phase of these compounds were derived from the standard molar energies of combustion, in oxygen, at T = 298.15 K, measured by static bomb combustion calorimetry. A Knudsen effusion method was used to perform the vapour pressure study of the referred compounds, yielding an accurate determination of the standard molar enthalpies and entropies of sublimation. The enthalpies of sublimation were also determined using Calvet microcalorimetry and the enthalpy and temperature of fusion were derived from DSC experiments. Derived results of standard enthalpy and Gibbs energy of formation in both gaseous and crystalline phases were compared with the ones reported in literature for fluorene. A theoretical study at the G3 and G4 levels has been carried out, and the calculated enthalpies of formation have been compared to the experimental values.     

The Thermodynamic Properties of Barium Uranoborate and Its Dihydrate

The standard enthalpies of formation of crystalline Ba(BUO₅)₂ and Ba(BUO₅)₂ · 2H2O at 298.15 K were determined by reaction calorimetry. The temperature dependences of the heat capacities of these compounds were studied over the temperature range 7–340 K by adiabatic vacuum calorimetry, and their thermodynamic functions were determined. The standard entropies and Gibbs functions of formation of these compounds at 298.15 K were calculated.     

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.