Ismael Mozo

Thermodynamics of 1-alkanol+linear alkanoate mixtures

1-Alkanol + linear alkanoate mixtures have been investigated in the framework of the DISQUAC model. The interaction parameters for the OH/COO contacts are reported. The quasichemical parameters are independent of the mixture compounds. The dispersive parameters change with the molecular structure of the components. The same behaviour is observed for the OH/CO (carbonyl) and OH/OCOO (carbonate) contacts. DISQUAC represents well the molar excess Gibbs energies, coordinates of azeotropes and molar excess enthalpies. Using binary parameters only, DISQUAC improves meaningfully predictions on this property from the UNIFAC model for 1-alkanol + linear alkanoate + hydrocarbon systems. In contrast, the Nitta–Chao and the DISQUAC models yield similar results for the thermodynamic properties of the binary and ternary mixtures considered. 1-Alkanol + linear alkanoate mixtures are characterized by strong dipolar interactions between like molecules. In 1-alkanol + CH3COO(CH2) u −1CH3 systems, dipole–dipole interactions between ester molecules are more important for u ≤ 7. For u ≥ 8, the more important contribution to the excess molar enthalpy comes from the disruption of the alkanol–alkanol interactions. For systems containing a polar compound such as alkanone, alkanoate or linear organic carbonate, dipolar interactions increase in the order: alkanone < alkanoate < carbonate.

Thermodynamics of mixtures containing alkoxyethanols. Part xxiii. Speed of sound predictions and ultrasonic studies of hydroxyether + organic solvent mixtures

The ability of different models to predict speeds of sound, u, of binary mixtures formed by alkoxyethanol and octane, oxaalkane or propylamine has been examined. The models applied are: the free length theory (LFT), the collision factor theory (CFT), and equations such as those proposed by Nomoto, Junjie or Van Dael. Collision factor theory, Nomotos and Junjies equations provide similar deviations between experimental and calculated u, which is represented quite accurately by these three models. Poorer predictions are obtained when applying the Junjies equation to propylamine systems, probably due to the existence of strong interactions between unlike molecules in such mixtures. In contrast, slightly better u predictions from CFT are obtained for the systems 2-methoxyethanol + polyether, or hydroxyether + propylamine. The good u predictions obtained using Nomotos equation remark the validity of Raos assumption on additivity of molar sound velocity contributions from atoms, atom groups and chemical bonds of the constituent molecules. Discrepancies between experimental and calculated u are larger when using FLT than those obtained from CFT, Nomotos or Junjies equations. This has been ascribed to association and size or shape effects. The linear dependence on the molar fractions of the component liquids of the Raos and Wadas constants suggests that there is no complex formation in the investigated mixtures, and that the interactions present in such systems are of dipolar type.

Thermodynamics of binary mixtures with strongly negative deviations from Raoult's Law. X. linear alkanoate + CHCl3 or + 1,1,2,2-tetrachloroethane

Mixtures formed by linear alkanoates and CHCl3 or 1,1,2,2-tetrachloroethane, which show strongly negative deviations from the Raoults law, have been studied in the framework of the dispersive–quasichemical (DISQUAC) model. Systems involving CH2Cl2; CCl4, Cl3C–CH3 or ClCH2–CH2Cl have also been briefly considered in order to carry out a more complete study. The corresponding interaction parameters are reported. As in other previous applications, the first (Gibbs energy) and third (heat capacity) quasichemical interaction parameters do not depend on the mixture components. DISQUAC represents fairly well vapor–liquid equilibria, VLE, and molar excess enthalpies, H E, of the systems considered. VLE of the methyl ethanoate + CHCl3 + benzene mixture is also well described by the model neglecting ternary interactions. UNIFAC (universal functional activity coefficient) fails when representing H E of systems containing very long alkanoates. The mixture structure is investigated using the concentration–concentration structure factor, S CC(0). Heterocoordination is prevalent even at very high temperatures.