Excess Molar Properties for Binary Systems of CnMIM-BF4 Ionic Liquids with Alkylamines in the Temperature Range (298.15 to 318.15) K. Experimental Results and Theoretical Model Calculations

Abstract

The experimental densities ρ and speeds of sound u for pure 1-hexyl-3-methylimidazolium tetrafluoroborate ([C6mim][BF4]), 1-octyl-3-methylimidazolium tetrafluoroborate ([C8mim][BF4]), butylamine (BA), and octylamine (OA) from (293.15 to 323.15) K and binary mixtures of the ionic liquids (ILs) with amines at (298.15, 308.15, and 318.15) K have been reported. The isentropic compressibilities, κS, Rao’s molar sound functions, R, intermolecular free lengths, Lf, excess molar volumes, VmE, and excess isentropic compressibilities, κSE for binary mixtures were derived. The VmE and κSE of the binary mixtures are negative and decrease with increasing temperature, with the exception of VmE being positive for [C6mim][BF4] and [C8mim][BF4] + OA in the high IL mole fraction region. The Prigogine–Flory–Patterson (PFP) theory has been applied to interpret the u and VmE data.