Insight into the solvation of sodium malonate in aqueous benzyltriethylammonium chloride solutions at different temperatures: A volumetric and viscometric study

The physicochemical properties of Ionic liquids (ILs) and organic salts must be studied to properly exploit them for industrial and research applications. The thermodynamic properties of aqueous organic salt solutions contribute to profound understanding of their interactions and applications. The present work has evaluated the possible molecular interactions of sodium malonate (SOMA) in aqueous benzyltriethylammonium chloride (BTEACL) within the molality range [ m BTEACL = (0.005-0.020) mol∙kg −1 ] at several temperatures (298.15, 303.15, 308.15 and 313.15 K) and pressure of 101 kPa. The experimental density, viscosity and speed of sound have been used to determine volumetric parameters [apparent molar volumes( V φ ), standard partial molar volume( V φ 0 ), apparent specific volumes( V φ SP ), the standard volume of transfer( Δ t V φ 0 ), Hepler’s constant [ ( ∂ V φ 0 / ∂ T ) P ], viscometric properties [viscosity B -coefficients, solvation number ( S n ), viscosity B -coefficient of transfer ( Δ t B ), free activation energy of the solvent and solute ( Δ μ 1 0 ≠ and Δ μ 2 0 ≠ ), entropy and enthalpy of activation ( Δ S 2 0 ≠ and Δ H 2 0 ≠ )] and compressibility properties [apparent molar isentropic compressibility of solute( K φ , S ), apparent molar isentropic compressibility of solute at infinite dilution ( K φ , S 0 )], respectively. Comprehensive computational investigations for binding energy, ESP mapping, FMO, Mülliken charge distribution and RDG analyses revealed strong electrostatic and non-covalent interactions between SOMA and BTEACL in the aqueous solutions. These findings demonstrated the structure-making effects of SOMA and the dominance of ion-solvent interactions in the ternary systems.