Measurements and molecular interactions for N,N-dimethylformamide with ionic liquid mixed solvents

Abstract

To understand the molecular interactions between N,N-dimethylformamide (DMF) with two families of ionic liquids (ILs), we have measured thermophysical properties such as densities (ρ) and ultrasonic sound velocities (u) over the whole composition range at 25°C under atmospheric pressure. The excess molar volume (V^E) and the deviation in isentropic compressibilities (ΔK_s) were predicted using these properties as a function of the concentration of IL. These results are fitted to the Redlich-Kister polynomials. The materials investigated in the present study included two families of ILs such as ammonium salts and imidazolium salts. Diethylammonium acetate ([Et₂NH][CH₃COO], DEAA), triethylammonium actetate ([Et₃NH][CH₃COO], TEAA), triethylammonium dihydogen phosphate ([Et₃NH][H₂PO₄], TEAP), and triethylammonium sulfate ([Et₃NH][HSO₄], TEAS) are ammonium salts and 1-benzyl-3-methylimidazolium chloride ([Bmim][Cl]) belongs to the imidazolium family. The intermolecular interactions and structural effects were analyzed on the basis of the measured and the derived properties. A qualitative analysis of the results is discussed in terms of the ion-dipole, ion-pair interactions, and hydrogen bonding between ILs and DMF molecules and their structural factors.