Thermodynamics of mixtures with strongly negative deviations from Raoult’s law. XII. Densities, viscosities and refractive indices at T = (293.15 to 303.15) K for (1-heptanol, or 1-decanol + cyclohexylamine) systems. Application of the ERAS model to (1-alkanol + cyclohexylamine) mixtures

Abstract

Densities, ρ, kinetic viscosities, ν, and refractive indices, nD, have been measured for (1-heptanol or 1-decanol+cyclohexylamine) systems at T=(293.15 to 303.15)K. The experimental ρ, ν, nD values were obtained using an Anton Paar DMA 602 vibrating-tube densimeter, an Ubbelohde viscosimeter and a refractometer model RMF970, respectively. These data are used to determine a number of derived properties: excess molar volumes, VmE, dynamic viscosities, η, deviations of this magnitude from linear dependence on mole fraction, Δη, Gibbs energies of activation of viscous flow, ΔG∗, deviations of nD from the ideal state, ΔnD, or molar refractions, Rm. In addition, (1-alkanol+cyclohexylamine) mixtures have been studied by means of the ERAS model. The corresponding parameters are reported. Viscosity data have been correlated by the following semi-empirical equations: Grunberg–Nissan, Hind, Frenkel, Katti–Chaudhri, Tamura–Kurata, Teja–Rice, McAllister and Heric. The deviations obtained are usually lower than 2%. The large negative VmE values of the studied solutions reveal the existence of strong alcohol-amine interactions. The properties VmE and Rm increase with the increasing of the chain length of the 1-alcohol, while Δη and ΔnD decrease. These variations suggest that interactions between unlike molecules are weakened and dispersive interactions become more important when the alcohol size increases. On the other hand, ΔG∗ is essentially determined by enthalpic effects. The effect of replacing cyclohexylamine by an isomeric amine, hexylamine (HxA), dipropylamine (DPA) or N,N,N-triethylamine (TEA) in mixtures with a given 1-alkanol is also investigated. It is shown that the strength of the methanol-amine interactions become stronger in the sequence: TEA<DPA<HxA≈cyclohexylamine. The application of the ERAS model to (1-alcohol+cyclohexylamine) mixtures supports these findings. The parameters obtained in this work fit well into the general ERAS treatment of (1-alkanol+amine) systems.