Apparent molar properties of benzyldimethylammonium based protic ionic liquids in water and ethanol at different temperatures

• New benzyldimethylammonium based protic ionic liquids (PILs) were synthesized.
• Density and speed of sound measured for PILs + water/ethanol binary mixtures.
• The apparent molar volume, Vϕ∞ follow the order: (PILs + ethanol) > (PILs + water).
• Excess volumes for PIL + ethanol mixtures are positive while for PIL + water are negative.

The apparent molar volumes, Vϕ and apparent molar isentropic compressibilities, Ks,ϕ of three benzyldimethylammonium based protic ionic liquids, namely, benzyldimethylammonium acetate (BDMAA), benzyldimethylammonium propionate (BDMAP), and benzyldimethylammonium hexanoate (BDMAH) in water and ethanol have been determined at T = (293.15, 298.15, 303.15, 308.15, 313.15 and 318.15) K and at ambient pressure from density, ρ and speed of sound, u measurements. The Redlich–Mayer type of equation has been used to calculate the apparent molar volume, Vϕ∞ and apparent molar isentropic compressibility, Kϕ∞ at infinite dilution, and the corresponding empirical parameters (Sv, Bv, Sk and Bk). The negative magnitude of limiting volumetric slopes, Sv versus m1/2 for (BDMAA + ethanol) binary solutions, suggests that BDMAA–ethanol interactions are strong. Further, the change in thermodynamic properties of binary solutions in relation to the alternation in the anionic structural constitution of protic ionic liquids has also been evaluated.

Apparent molar volume (Vϕ) versus molality (m) of benzyldimethylammonium propionate (BDMAP) in (BDMAP + ethanol) binary solution at different temperatures.Figure optionsDownload as PowerPoint slide