Experimental and quantum-chemical methods were used to determine the thermodynamic properties of one of the representatives of the 1,6-diazabicyclo[4.1.0]heptane molecular system which is of interest in design of new promising high-energy density materials. The combustion energy of this compound at 298.15 K was measured using isoperibolic macrocalorimeter with a static bomb. The enthalpy of sublimation was determined by Knudsen cell mass spectrometry method. The heat capacity in the range of 6-350 K was studied using vacuum adiabatic calorimetry. No phase transitions were found by analyzing the behavior of the heat capacity curve. It has been shown that purification of a substance by recrystallization can lead to encapsulation of the solvent inside the crystalline structure. Using high-level quantum chemical calculations, the enthalpy of formation and thermodynamic functions of this compound in the gas phase were obtained. When calculating thermodynamic functions, the conformational isomerism of the studied molecule was taken into account. As a result, a complete set of standard thermodynamic functions was obtained for the studied compound, including formation functions, both in the crystalline and gaseous phases over a wide temperature range.

Heat capacities of 2-furfurylamine were measured by low-temperature adiabatic calorimetry in the temperature range from 5.6 to 356.1 K. Two phase transitions, solid phase transition and melting, were revealed at temperatures of 180.4 K and 228.17 K. Thermodynamic characteristics determined from experimental data show that the mechanism of solid phase transition is intermediate between order-disorder and displacive type. This conclusion is in agreement with X-ray crystallography data (Seidel et al., 2019). The standard thermodynamic functions in the condensed state (molar heat capacity, enthalpy, entropy and Gibbs energy) were calculated in the temperature range 5 - 350 K. Using the determined value of entropy for liquid 2-furfurylamine and available value of fH degrees m(l), the properties of formation, fS degrees m(l) and fG degrees m(l), were obtained. The thermodynamic functions of gaseous 2-furfurylamine were calculated taking into account the internal rotation in this molecule. The required molecular constants were determined from quantum chemical calculations.

The bicyclic diaziridine derivative 6-(4-methoxyphenyl)-1,5-diazabicyclo[3.1.0]hexane was synthesized, purified and characterized. Its standard specific energy in the crystalline state at 298.15 K was determined by static bomb combustion calorimetry, from which the standard enthalpies of combustion and formation were calculated. The enthalpy of formation in the gas phase was calculated using the DLPNO-CCSD(T1)/CBS method in combination with isodesmic reactions; the molecular electrostatic potential and group additivity methods were used to estimate the enthalpy of sublimation.

A comprehensive study of the thermodynamic properties of two ionic liquids 1-ethyl-3-methylimidazolium (EmimMS) and 1-butyl-3-methylimidazolium methanesulfonate (BmimMS) was carried out. The isobaric heat capacity of the crystal and liquid phases of EmimMS and BmimMS was determined in the temperature range from 80 to 380 K by vacuum adiabatic calorimetry. The heat capacities of EmimMS and BmimMS were assessed at temperatures from 5 to 80 K by the Kelly method. The temperature dependencies of EmimMS and BmimMS main thermodynamic functions were determined in the temperature range from 5 to 380 K (isobaric heat capacity Cp,m(T), standard entropy So m(T), heat content Ho m(T) - Hom(0), Gibbs energy content Go m(T) - Hom(0). Melting points and fusion enthalpies of EmimMS and BmimMS have been refined by DSC. The enthalpies of dissolution in water of EmimMS and BmimMS at 298.15 K were measured by the dissolution calorimetry. The standard enthalpies, entropies and Gibbs energies of EmimMS and BmimMS formation in the crystal and liquid state at 298.15 K were calculated from the experimental data. Comparison of the obtained thermodynamic characteristics with the literature data was carried out.

Knudsen cell mass spectrometry was used to study the evaporation of two ionic liquids, 1-ethyl-3-methylimidazolium methanesulfonate ([EtMIm][MS], MS = CH3SO3) and 1-butyl-3-methylimidazolium methanesulfonate ([BuMIm][MS]), accompanied by thermal decomposition (thermolysis). The independent occurrence of evaporation and thermolysis reactions made it possible to determine their thermodynamic and kinetic characteristics under identical experimental conditions. The saturated vapor pressures were measured and the standard enthalpies of vaporization of [EtMIm][MS](l) and [BuMIm][MS](l) were obtained. The standard thermodynamic functions of formation in the liquid and gaseous states at 298.15 K were estimated from the available experimental data and the results of quantum chemical calculations. The gaseous decomposition products of ionic liquids were identified and the pressures of the thermolysis products of [EtMIm][MS](l) were determined. According to the experimental data and quantum chemical calculations, the thermolysis of [EtMIm][MS](l) occurs through heterogeneous reactions far from the equilibrium state. The kinetics of the reactions is described in two ways. When the degree of sample conversion is used as a variable, the constant reaction rates at the initial stage of thermolysis correspond to a pseudo-zero order reaction with a monotonic increase in the degree of conversion. In the proposed alternative approach, the reaction rates are estimated from the fluxes of thermolysis products and are expressed in terms of ionic liquid concentration.

The standard molar enthalpies of formation in the gas phase at T = 298.15 K for 43 furan derivatives were calculated using the DLPNO-CCSD(T-1)/CBS method in conjunction with isodesmic-type reactions to assess the accuracy of experimental data reported in the literature. The high accuracy of the experimental data was confirmed for almost half of the studied compounds (44%). For the remaining furans, the discrepancy between the experimental and theoretical values is larger than 5-70 kJmol(-1), and additional experimental measurements are obviously required to determine more accurate values of the enthalpy of combustion and/or enthalpy of phase change. The experimental enthalpies of formation of 12 furans are recommended as benchmark reference values for use in thermochemical calculations of furan-based compounds.

A comprehensive thermodynamic study of two ionic liquids EmimCl and BmimCl were carried out by experimental and calculation methods. Isobaric heat capacity of crystal and liquid EmimCl was determined by low temperature vacuum adiabatic calorimetry in the temperature range from 8 to 376 K. Experimental heat capacity curve of crystal EmimCl and literature data of BmimCl were fitted by linear combination of Einstein's functions and were integrated; as a result, the following thermodynamic functions for EmimCl and BmimCl were calculated: standard entropy S0m(T), heat content H0m(T)-H0m(0) and Gibbs energy G0m(T)-H0m(0). Melting parameters of these substances were measured by DSC and adiabatic calorimetry. Standard enthalpies of dissolution of crystal EmimCl and BmimCl in water at 298.15 K were measured by isothermal solution calorimetry. Based on these data, standard enthalpies, entropies and Gibbs energies of formation were calculated for crystal and liquid phases of EmimCl and BmimCl at 298.15 K. Standard enthalpies of EmimCl and BmimCl formation in the gaseous state at 298.15 K were defined via quantum chemistry methods. The analysis and comparison of the obtained thermodynamic characteristics with the literature data was carried out.

The combustion energy and standard molar enthalpy of formation of liquid furfurylamine were determined using an isoperibol calorimeter with a static bomb. The theoretical calculations were used for the interpretation of experimental calorimetric result. The DLPNO-CCSD(T1)/CBS method in conjunction with isodesmic-type reactions was used to calculate the gas-phase enthalpy of formation of this compound. At the same level of theory, the interconversion of the gauche and anti conformers of furfurylamine and the N-H & BULL;& BULL;& BULL;N hydrogen bonding between them leading to the association into dimeric units were studied. The calculated values of equilibrium and rate constants for reaction gauche & RARR; anti and enthalpy of dimerization of two conformers suggest that the gaseous furfurylamine exists predominantly in the dimeric form. An additional support for the strong association of furfurylamine in the vapor phase was obtained from comparison of the enthalpies of formation in liquid and gaseous states: the consistency between these two values was achieved only when a correction for dimerization was applied.

The combustion energy and standard molar enthalpy of formation of crystalline 6-phenyl-1,5-diazabicyclo[3.1.0]hexane (PDABH) were determined using an isoperibolic calorimeter with a static bomb. PDABH is the first diaziridine for which the experimental value of the enthalpy of formation was obtained. This value was validated by the theoretical values of gas phase enthalpy of formation and enthalpy of sublimation. The gas phase enthalpy of formation was calculated using the DLPNO-CCSD(T1)/CBS method in conjunction with isodesmic-type reactions. This method was chosen in comparison to another high quality evaluative method (G4), which has been shown to provide unreliable results for cyclic nitrogen containing compounds. The descriptors of the molecular electrostatic potential (MEP) were used to estimate the enthalpy of sublimation of PDABH. The proposed MEP model is based on experimental enthalpies of sublimation for 75 compounds structurally similar to PDABH. The high-level ab initio calculations of gas phase enthalpies of formation combined with enthalpies of sublimations estimated using descriptors of MEP allow predicting the enthalpies of formation of diaziridines in the solid phase.

Differential scanning calorimetry is used to study the temperature and enthalpy of melting of L‑asparagine monohydrate. Its thermal stability is estimated. Low-temperature adiabatic calorimetry is used to measure heat capacity in the 8–355 K range of temperatures. An anomaly in the heat capacity curve is detected in the region of 265–275 K and studied. A single crystal X-ray diffraction study of the sample is performed in the 113–281 K range of temperatures. The main thermodynamic functions and the functions of formation in the condensed state are calculated at 298 K using the experimental and literature data.

The liquid phase standard molar enthalpy of formation of 2-methyltetrahydrofuran was determined by isoperibolic calorimetry of combustion. The purity of the sample was determined by the g.l.c and the cryoscopic methods. Using available enthalpy of vaporization, the gas phase enthalpy of formation was obtained. This value agrees well with that calculated by DLPNO-CCSD(T1)/CBS method. (c) 2021 Elsevier Ltd.

Thermodynamic data for the crystalline phase of indium were critically assessed using an extended Einstein model from 0 K. The heat capacity between 6 K and 354 K was measured using an automated vacuum adiabatic calorimeter to compensate for a lack of published data between 21 K and 273 K. Data for the liquid phase were described using a two state model. During the assessment, careful analysis of the experimental data was carried out. In order to derive a precise value for So298 an additional technique using multiple Einstein functions was used, which allows the experimental heat capacity and enthalpy data for the solid phase to be approximated accurately from 0 K up to the melting point.

The heat capacity and phase transitions of 2-methyltetrahydrofuran in the temperature range from 7 to 350 K were measured using adiabatic calorimetry. The smoothed molar thermodynamic functions in the condensed state were determined on the basis of these measurements. The thermodynamic functions of the formation were also calculated. The gas-phase entropy at 298.15 K was obtained using the entropy of crystal 2-methyltetrahydrofuran, entropy of fusion and entropy of vaporization. This entropy value was used to clarify some aspects of the discrepancies between the interpretations of pseudorotation in 2-methyltetrahydrofuran. An extended quantum chemical study of pseudorotation in 2-methyltetrahydrofuran was undertaken to provide additional insight into the conformational features of a molecule. The contribution of pseudorotation to the entropy was calculated for different pseudorotational potentials constructed using various theoretical models. The experimental entropy value is in best agreement with intramolecular conversion between two low energy conformers connected by the transition state with an energy of about 4 kJ mol(-1). The standard thermodynamic properties of 2-methyltetrahydrofuran in the gaseous state (T = 100 K to 1500 K) were calculated using experimental and theoretical molecular parameters.

The energies of combustion of crystalline 1-methyl-2,3,3-triphenylcyclopropene (C22H18), methyl2,3-di phenylcycloprop-2-ene-1-carboxylate (C17H14O2) and 1,2,3-triphenylcyclopropene (C21H16), were determined in isoperibolic calorimeter at T = 298.15 K. The enthalpies of sublimation were measured by isothermal heat-conducting differential microcalorimeter ("Setaram") at T = 298.15 K. The enthalpies of formation in the crystalline and gaseous states were calculated. The values of enthalpies of three group contributions: [C-(Cd)2(Cb)2], [C-(Cd)2(CO)(H)] and [C-(Cd)2(Cb)(H)], which absents in the Cohen additive scheme, were estimated. (C) 2021 Elsevier Ltd.

Molar heat capacity of ammonium methanesulfonate NH4SO3CH3 was measured in the temperature range from 8.51 to 345.47 K by low-temperature vacuum adiabatic calorimetry. Heat capacity and the main thermodynamic functions (heat content, entropy and Gibbs energy) of NH4SO3CH3 in solid state were tabulated as a function of temperature from 10 K to 340 K. Enthalpy of NH4SO3CH3 dissolution in water was determined at 298.15 K by means of solution calorimetry. On the basis of the experimental data, the standard entropy, enthalpy and Gibbs energy of NH4SO3CH3 formation at 298.15 K were calculated. A second-order phase transition of NH4SO3CH3 was observed by adiabatic calorimetry at T = 272.6 +/- 0.5 K. (C) 2021 Elsevier Ltd.

The heat capacity of 2-methylfuran in the temperature range of 8-350 K was determined by vacuum adiabatic calorimetry. The temperature, the enthalpy and the entropy of fusion and purity of investigated sample were determined by fractional melting. The smoothed thermodynamic functions (changes in enthalpy, entropy and Gibbs energy) in the region of 8-350 K were calculated. The entropies of formation and Gibbs energies of formation of 2-methylfuran at 298.15 K in the liquid and ideal gas states were found, using the literature data. (c) 2021 Elsevier Ltd.

The energy of combustion of liquid 1,3,3-trimethylcyclopropene was obtained in isoperibolic calorimeter at T = 298.15 K. The saturated vapour pressures were determined by the comparative ebulliometry in the temperature range 295-310 K. The normal boiling temperature and the enthalpy of vaporization were estimated based on p-T -data. The enthalpy of vaporization was measurement by calorimetric method at T = 298.15 K. The density was determined by pycnometric method at T = 293.15 K. The formation enthalpies of the compound in liquid and gas states were determined using the obtained experimental data. The enthalpies of formation in the gaseous state for cyclopropene and its methyl-substituted derivatives were estimated by G4 method. (c) 2020 Published by Elsevier Ltd.

Segregation of particles in a nanodiamond aqueous colloid due to Stokes’ law leads to re-ordering of the lattice of particles.

Thermodynamic data for crystalline white and grey tin were assessed using an extended Einstein model from 0 K. Ab-initio simulations in the framework of density functional theory (DFT) with the quasiharmonic approximation (QHA) were carried out to define the heat capacities for both phases of tin from 0 K up to room temperatures. Good agreement was observed between theoretical and experimental heat capacities, which makes it possible to combine theoretical and experimental data to determine the standard entropies. Data for the liquid phase were described using a two state model. During the assessment, careful analysis of the experimental data was carried out. In order to fulfil the need for a precise evaluation of S-298(o) we needed to use an additional technique using multiple Einstein functions, which allows the experimental heat capacity and enthalpy data for the solid phase to be approximated accurately from 0 K up to the melting point and to estimate solid phase transition entropy and enthalpy which are difficult to measure due to a high activation barrier. Additional measurements of heat capacity were carried out where existing data were scarce.

The combustion energy of crystalline copper(II) pivalate was determined by static-bomb isoperibolic calorimetry. The standard enthalpy of formation was calculated on basis of obtained results. The value of standard enthalpy of formation was used to calculate the enthalpy of breaking bond Cu-Piv by the reaction: Cu(C5H9O2)(2)(cr) = Cu(cr) + 2C(5)H(9)O(2)(g) and the enthalpy of formation of the trimer Cu-3(Piv)(6) in the gaseous state. (C) 2018 Elsevier Ltd.