Solvation properties of acetaminophen in aqueous ionic liquid, 1-hexyl-3-methylimidazolium bromide, solutions at different temperatures

Abstract

Densities, speeds of sound and molar conductivities of acetaminophen in 0.1, 0.2, 0.3 and 0.4mol.kg−1 aqueous solution of ionic liquid, 1-hexyl-3-methylimidazolium bromide ([HMIm]Br), against the molality of acetaminophen have been measured at T=(293.15 to 308.15) K. Using the density and speed of sound data, standard partial molar volume (Vϕ0) and partial molar isentropic compressibility (Kφ,s0) have been calculated. These parameters have been used to calculation transfer volume and transfer compressibility for acetaminophen from water to aqueous ionic liquid solution. The transfer quantities are positive and increase with increasing molality of the ionic liquid and decrease with temperature which indicate the dominance of ion or hydrophilic–hydrophilic interactions between [HMIm]Br and acetaminophen and dehydration effect of ionic liquid on the acetaminophen solutions. To confirm the above results, the limiting molar conductivities (Λ0) and ion association constants (Ka), for [HMIm]Br in aqueous acetaminophen solutions have been estimated. The association constants were also used to obtain the thermodynamic functions of ion association process of the ionic liquid.