Experimental and theoretical excess molar properties of imidazolium based ionic liquids with molecular organic solvents – I. 1-Hexyl-3-methylimidazlouim tetraflouroborate and 1-octyl-3-methylimidazlouim tetraflouroborate with cyclic ethers

Abstract

Experimental densities, ρ, speeds of sound, u, and refractive indices, nD for pure 1-hexyl-3-methylimidazolium tetrafluoroborate ([C6mim][BF4]), 1-octyl-3-methylimidazolium tetrafluoroborate ([C8mim][BF4]), 1,4 Dioxane (DO) and (THF) between the temperature (293.15 to 323.15K) at 5K interval and their binary mixtures at T=(298.15, 308.15 and 318.15)K at entire range of composition have been measured using an Anton-Paar DSA 5000 and Abemmete refractometer. Experimental measurements were used to estimate Rao’s molar sound functions, R, excess molar volumes, VmE, excess molar isentropic compressibilities, κs,mE, refractive indices deviations ΔϕnD and deviation in molar refraction, ΔRm. Excess properties have been fitted to the Redlich–Kister polynomial equation and binary coefficients were obtained. VmE and κs,mE were observed to be negative and decrease with increasing temperature, whereas ΔϕnD was found to be positive and increases with temperature over the entire composition range. Equations of state and several mixing rules were used to predict refractive indices of the binary mixtures and compared with the experimental values by means of the standard deviation and found to be in excellent agreement. Intermolecular interactions between the unlike molecules of the mixtures have been discussed by well known arguments. Excess molar volumes of the binary mixtures have been analyzed by Prigogine–Flory–Patterson (PFP) theory and results were compared with the experimental results.