Exploring the interactional behavior of N-acetylcysteine in aqueous-dimethylsulfoxide solutions: A physicochemical and computational study

• Density and viscosity data of NAC + H 2 O + DMSO. • Related parameters of volume and viscosity for NAC in DMSO, H 2 O, & DMSO-H 2 O mixture have been determined. • NAC behaves as structure maker in H 2 O, DMSO and aqueous dimethylsulfoxide solution. • Viscosity values based on Eyring's equation. • Results presented in terms of solute-solute and solute-solvent interactions. Density and viscosity data of NAC + H 2 O + DMSO. Related parameters of volume and viscosity for NAC in DMSO, H 2 O, & DMSO-H 2 O mixture have been determined. NAC behaves as structure maker in H 2 O, DMSO and aqueous dimethylsulfoxide solution. Viscosity values based on Eyring's equation. Results presented in terms of solute-solute and solute-solvent interactions. In order to determine the molecular interactions, the volumetric and viscometric characteristics of N-Acetyl-L-Cysteine (NAC) (∼0.10 to ∼1.00) mol.kg −1 solutions in water, dimethylsulfoxide (DMSO), and aqueous solution of DMSO (DMSO-H 2 O) have been investigated at temperatures between 298.15 and 318.15 K at 5 K interval. From the density data Apparent molar volume ( φ v ), apparent molar expansivity ( φ E 0 ), apparent molar volume at infinite dilution ( φ v 0 ), and transfer apparent molar volume ( φ v , t r 0 ) have been evaluated. Apparent molar volume ( φ v ) of NAC decreased for all the investigated systems with concentration but increased with temperatures. Negative S v values for all the systems indicate the weak solute-solute interactions. Positive and small negative values of Hepler constant, (∂ 2 φ v 0 / ∂ T 2 ) showed that NAC possess structure-making capabilities in ternary solutions. With increasing the concentration of NAC viscosities of all the solutions increased but decreased as the temperature rises. Viscosity coefficient (B, D), as well as the derivative of the B coefficient, ( ∂ B / ∂ T ) , values have been calculated using the viscosity data and demonstrated the structure making properties of the investigated systems. Thermodynamic characteristics such as change in free energy (ΔG∗), change in enthalpy (ΔH∗), and change in entropy (ΔS∗) for viscous flow have established that all the processes are nonspontaneous at low temperatures and spontaneous at high temperatures. Computational analysis also confirmed that the solution is being formed by a hydrophilic bond through solute-solvent interaction.