A comprehensive analysis of the thermochemical properties of levoglucosan, using static bomb combustion calorimetry, Knudsen effusion technique, and differential scanning calorimetry, is presented. The experimental results allow us to derive the enthalpy of formation, in the gaseous phase, and thereafter to do a comparison with the same parameter obtained computationally. The good agreement between the experimental and computational results gives confidence to our determinations, particularly when they are compared with others already reported in literature. After testing the computational methodology, the ionization energy, electron affinity, proton affinity, gas-phase basicity, gas-phase acidity, and bond dissociation enthalpies of levoglucosan were also obtained. The presence of intramolecular hydrogen bonds in the most stable conformation of levoglucosan was verified by applying Quantum Theory of Atoms in Molecules calculations. Furthermore, a joint differential scanning calorimetry and temperature dynamic Fourier transform infrared (FT-IR) spectroscopic study was used to study the crystalline phase of levoglucosan between 298.15 K and the melting temperature.

Isothermal vapor−liquid equilibrium (VLE) for thiophene + n-hexane at (338.15 and 323.15) K and thiophene + 1-hexene at (333.15 and 323.15) K were measured with a circulation still. Maximum pressure azeotropes were found in the thiophene + n-hexane system. Azeotropic behavior was not found for the thiophene + 1-hexene system. The experimental results were correlated with Wilson model and also compared with original UNIFAC, UNIFAC−Dortmund, and COSMO-RS predictive models. Analyses of liquid and vapor-phase composition were determined with gas chromatograph and refractometer. All VLE measurements passed the three thermodynamic consistency tests used.

Vapor−liquid equilibrium (VLE), excess molar enthalpies (H E ), and excess molar volumes (V E ) provide means of developing accurate thermodynamic models. In this work, new data of binary mixtures of ethyl acetate, butyl acetate, and 2-butanol are reported. Isothermal VLE data at 350 K were measured by using a circulation still for ethyl acetate + 2-butanol, for 2-butanol + butyl acetate, and for ethyl acetate + butyl acetate. H E was measured at 298 K by using a SETARAM C80 calorimeter equipped with a flow mixing cell. V E was measured at 298 K by using an Anton Paar DMA 512P densimeter. Liquid phase activity coefficients of the Wilson model and vapor phase fugacities of the Hayden−O'Connell correlation were regressed for a thermodynamic model based on the measured data. Model extrapolation agreed well with literature data. Redlich−Kister equation parameters were regressed by using only the measured V E data.

This work presents a comprehensive evaluation of the phase behaviour and cohesive enthalpy of protic ionic liquids (PILs) composed of 1,5-diazabicyclo[4.3.0]non-5-ene (DBN) or 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) organic superbases with short-chain length (acetic, propionic and butyric) carboxylic acids. Glass transition temperatures, T, and enthalpies of vaporization, ΔH, were measured for six [BH][A] (1 : 1) PILs (B = DBN, DBU; A = MeCOO, EtCOO, nPrCOO), revealing more significant changes upon increasing the number of -CH- groups in the base than in the acid. The magnitude of ΔH evidences that liquid PILs have a high proportion of ions, although the results also indicate that in DBN PILs the concentration of neutral species is not negligible. In the gas phase, these PILs exist as a distribution of ion pairs and isolated neutral species, with speciation being dependent on the temperature and pressure conditions - at high temperatures and low pressures the separated neutral species dominate. The higher T and ΔH of the DBU PILs are explained by the stronger basicity of DBU (as supported by NMR and computational calculations), which increases the extent of proton exchange and the ionic character of the corresponding PILs, resulting in stronger intermolecular interactions in condensed phases.

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