Molecular Interactions of Diphenhydramine-hydrochloride with Some Imidazolium-Based Ionic Liquids in Aqueous Media at = 293.15-313.15 K: Volumetric, Acoustic, and UV Absorption Studies.

From the density () and speed-of-sound () measurements, the interactions of the drug diphenhydramine-hydrochloride (DPH) with three imidazolium-based ionic liquids (ILs) (1-butyl-3-methylimidazolium chloride, [Cmim][Cl], 1-hexyl-3-methylimidazolium chloride1, [Cmim][Cl], and 1-methyl-3-octylimidazolium chloride, [Cmim][Cl]) have been investigated in aqueous medium at = 293.15-313.15 K and experimental pressure = 0.1 MPa. From the density calculations, the apparent molar volume ( ) and the apparent partial molar volumes of transfer (Δ ) have been determined for various solutions of DPH in aqueous solutions of different ILs. In addition, from the speed-of-sound data, the apparent molar isentropic compressibility ( ), apparent partial molar isentropic compressibility ( ), and apparent partial molar isentropic compressibility of transfer (Δ ) have been calculated. The pair and triplet interaction coefficients are derived from apparent partial molar volumes of transfer. For the present mixtures, the absorption spectra have been also recorded using a UV-visible spectrophotometer. Using Hepler's constant, the structure-making nature of the solute has been confirmed. All these calculated parameters provide detailed insights into various physicochemical interactions prevailing in the ternary system and confirm the presence of a strong attractive interaction between DPH and ILs.