Volumetric, Acoustic and Conductometric Studies of Acetaminophen in Aqueous Ionic Liquid, 1-Octyl-3-methylimidazolium Bromide at T = 293.15-308.15 K

Abstract

The density (<em>d</em>), speed of sound (<em>u</em>) and electrolytic conductivity (Λ) for systems containing acetaminophen, ionic liquid {1-octyl-3-methyl imidazolium bromide, [OMIm] Br} and water have been measured at <em>T</em> = 293.15-308.15 K. The measured data have been applied to calculate, standard partial molar volume ( ), Hepler's constant , apparent molar isentropic compressibility (<em>K_φ</em>), transfer volume ( ), transfer compressibility ( ) and hydration number (<em>n_H</em>), and used to discuss various solute-solvent interactions. The transfer quantities are positive and increase with molalities of ionic liquid and decrease with temperature, indicating the dominance of hydrophilic-hydrophilic interactions between the ionic liquid and acetaminophen, and dehydration effect of ionic liquid on the solutions. The limiting molar conductivities ( ) and ion association constants (<em>K_a</em>) for [OMIm]Br in aqueous acetaminophen solutions have been estimated using low concentration Chemical Model (lcCM). The Ka values were also used to obtain the thermodynamic functions of association process. Thermodynamic results show that the formation process of ion association of the ionic liquid has endothermic nature and is driven by the change in entropy.