Exploration of Assorted Interactions of Dopamine Hydrochloride and (±)-Epinephrine Hydrochloride in Aqueous Acetophenone Solutions by Physicochemical and Computational Investigations at Different Temperatures

We investigated the physicochemical properties of dopamine hydrochloride (DAH) and (±)-epinephrine hydrochloride (EPH) in aqueous solutions of acetophenone (ACP). Measurements of density (ρ), viscosity (η), surface tension (γ), and refractive index (nD) were taken at varying concentrations (0.001, 0.003, 0.005 mol·kg–1) and temperatures (298.15 K, 308.15 K, 318.15 K) under atmospheric pressure (0.1 MPa). The solute–solute and solute–solvent interactions between DAH and EPH with aqueous ACP drug solutions were analyzed using the limiting apparent molar volumes (Vϕ0) obtained from the Masson equation, the viscosity parameters, A and B coefficients, and molar refraction (RM) from the Lorentz–Lorenz equation. The determination of interactions related to the ternary systems, (DAH + aq. ACP) and (EPH + aq. ACP), can also benefit from the use of transfer volumes (ΔVϕ0) and interaction parameters (VAB, VABB). Various thermodynamic parameters, such as Δμ10#, Δμ20#, TΔS20#, and ΔH20# suggest that there are significant molecular interactions in the system being studied. Findings from UV–vis spectroscopy also support our experimental and theoretical results. The optimization energy calculated through computational analysis using the density functional theory verifies the stability of the molecular structures in the ternary systems (DAH + ACP + H2O) and (EPH + ACP + H2O), thus confirming the experimental findings.