Volumetric and acoustic approach for investigating molecular interactions of choline acetate ionic liquid in α,ω-alkanediols at different temperatures

Abstract

Various thermophysical parameters such as density ρ, ultrasonic sound velocity u, refractive index nD, and specific conductivity κ of 2-hydroxyethyl-trimethylammonium acetate; [(C2H4OH)-(CH3)3N] [Acetate] or Choline Acetate in α,ω-alkanediols viz. 1,2-Ethanediol (1,2-ED), 1,3-Propanediol (1,3-PPD), 1,4-Butanediol (1,4-BTD) and 1,5-Pentanediol (1,5-PTD) have been investigated over various concentrations (0.02–0.4 mol/kg) and at temperatures ranging from 293.15 to 323.15 K at atmospheric pressure. In order to determine the effect of OH spacing in α,ω-alkanediols on the molecular interactions in solutions, the thermodynamic properties and derived parameters at infinite dilution such as apparent molar volumes Vϕ, apparent molar compressibilities KSϕ, apparent molar volume at infinite dilution Vϕ0 , limiting apparent molar expansibilities ϕE0, limiting isentropic compression KSϕ0 have been calculated. The calculated parameters in the mixtures have been interpreted in terms of increasing hydrophobicity due to the successive addition of –CH2 unit in α,ω-alkanediols. The results have been further supported using polarizability (α) and conductivity studies. The experimental observations have also been supported by DFT calculations in terms of the interaction energies of cation and anion of Choline Acetate in solutions containing α,ω-alkanediols.