Investigation on the Molecular Interaction of N-Acetylcysteine in Aqueous Dimethyl Sulfoxide Systems and Thermoacoustic Properties at Various Temperatures

The potential molecular interactions among N-acetyl-l-cysteine (NAC), water (H₂O), dimethyl sulfoxide (DMSO), and aqueous dimethyl sulfoxide (DMSO-H₂O) were investigated from the experimental speed of sound (c) and density values (ρ) over the temperature range from 298.15 to 318.15 K and at atmospheric pressure. The acoustic parameters, viz., isentropic compressibility (κ_s), apparent molar isentropic compressibility (κ_s,ϕ), limiting apparent molar isentropic compressibility (κ_s,ϕ⁰), S_k, acoustic impedance (Z), hydration number (N_H), and relative association (R_A), were determined using experimental sound velocities. The results were interpreted in terms of possible solute–solute and solute–solvent interactions. Negative κ_s,ϕ values identifying molecules of water in the bulk solution seemed to be more compressible than those surrounding the ionic charges of the solute. κ_s, κ_s,ϕ⁰, and Z values indicate the presence of solute–solvent interaction, whereas S_k values specify that solute–solute interaction is also present in the studied system.