Physicochemical properties of ammonium acetate / propionic acid as a novel deep eutectic solvent and its binary...

Emergence of deep eutectic solvents as potential replacements for volatile organic solvents has attracted interest of the scientific community in diverse fields of applications. Compared to ionic liquids, which exhibit similarity in many respects with this new class of green solvents, deep eutectic solvents (DESs) show low toxicity, and are easy to prepare from cheap and abundantly available starting materials. Knowledge of physicochemical properties of DESs is a prerequisite for their safe applications in technological fields and to understand the nature of interactions present in these systems. Although physicochemical properties of choline chloride based DESs are widely investigated, similar information on ammonium acetate based DESs is scant. In this work, a novel ammonium acetate/propionic acid deep eutectic solvent (AA/PA DES) is reported which is prepared by mixing ammonium acetate (AA) and propionic acid (PA) in the 1:3 mol ratio and characterized by FTIR, ¹H and ¹³C NMR, TGA and DSC techniques. The density (ρ), sound velocity (u), viscosity (η) and conductivity (κ) of the pure DES and its binary mixtures with water are investigated over the entire composition range and temperatures (298.15-353.15) K. The excess properties, V_m^E, K_S^E, Δη, and ΔG^*E are calculated and corelated using Redlich-Kister equation (RKE). Temperature dependence of conductivity and viscosity is satisfactorily described by the Vogel - Fulcher - Tamman (VFT) equation rather than Arrhenius equation. The pure DES shows a wide electrochemical potential window ranging from - 1000 mV to + 1000 mV, which coupled with its better solubilizing characteristics, could be exploited for electrochemical work.