Investigation of thermo physical behaviour of deep eutectic solvent binary mixtures with 2-ethyl-1-hexanol and 2-ethyl-1-butanol DES (choline chloride/propanoic acid) with 2-ethyl-1-hexanol and 2-ethyl-1-butanol)

This study investigates the thermophysical behaviour of binary liquid mixtures comprising a deep eutectic solvent (DES) of choline chloride and propanoic acid (1:2 molar ratio) with two alcohols: 2-ethyl-1-hexanol and 2-ethyl-1-butanol. Measurements were performed at various temperatures and compositions. Experimental values of density (ρ), ultrasonic velocity (u) and viscosity (η) were used to calculate excess molar volume (VE), deviation in isentropic compressibility (∆κs) and viscosity deviation (Δη) to understand molecular interactions. Negative VE and ∆κs values over most compositions indicate strong interactions between unlike molecules, suggesting tighter packing due to hydrogen bonding, dipole–dipole interactions and structural compactness. The Jouyban–Acree model was applied to correlate experimental and predicted values, showing good agreement and demonstrating its suitability for these systems. The findings enhance understanding of interaction dynamics in DES–alcohol mixtures and support the application of such green solvents in sustainable chemical processes.