Thermodynamics Research Center / ThermoML | Journal of Chemical Thermodynamics

ABSTRACT

Densities and viscosities (eta) of binary mixtures containing the Protic Ionic Liquid (PIL), pyrrolidinium octanoate with five molecular solvents: water, methanol, ethanol, n-butanol, and acetonitrile are determined at atmospheric pressure as a function of the temperature and within the whole composition range. The refractive index of all mixtures (nD) is measured at 298.15 K. The excess molar volumes VE and deviation from additivity rules of viscosities etaE and refractive index del-phin, of pyrrolidinium octanoate solutions were then deduced from the experimental results as well as apparent molar volumes Vphii, partial molar volumes View the MathML source and thermal expansion coefficients. The excess molar volumes VE are negative over the entire mole fraction range for mixture with water, acetonitrile, and methanol indicating strong hydrogen-bonding interaction for the entire mole fraction. In the case of longest carbon chain alcohols (such as ethanol and n-butanol) + pyrrolidinium octanoate solutions, the VE variation as a function of the composition describes an S shape. The deviation from additivity rules of viscosities is negative over the entire composition range for the acetonitrile, methanol, ethanol, and butanol, and becomes less negative with increasing temperature. Whereas, etaE of the {[Pyrr][C7CO2] + water} binary mixtures is positive in the whole mole fraction range and decreases with increasing temperature. the excess Gibbs free energies of activation of viscous flow for these systems were calculated. The deviation from additivity rules of refractive index del-phin are positive over the whole composition range and approach a maximum of 0.25 in PIL mole fraction for all systems. The magnitude of deviation for del-phin describes the following order: water greater than methanol greater than acetonitrile greater than ethanol. Results have been discussed in terms of molecular interactions and molecular structures in these binary mixtures.