Density and ultrasonic sound speed measurements for N,N-dimethylformamide with ionic liquids

To understand the molecular interactions between N,N-dimefhylformamide with two families of ionic liquids, the thermophysical properties such as densities and ultrasonic sound speeds have been measured over the entire composition range at 25 °C under atmospheric pressure. The materials investigated in the present study include two families of ionic liquids, viz., ammonium salts and imidazolium salts. Diethyl ammonium acetate, triethyl ammonium acetate, triethyl ammonium dihydrogen phosphate and triethyl ammonium sulphate are the ammonium salts while 1-benzyl-3-methylimidazolium chloride belongs to the imidazolium family. The intermolecular interactions and structural effects are analyzed on the basis of the measured and derived properties. A qualitative analysis of the results are discussed in terms of the ion-dipole interactions, ion-pair interactions and hydrogen bonding between the ionic liquids and N,N-dimethylformamide molecules.