Exploration of Solvation Consequences of Nicotinic Acid (Vitamin B3) Prevailing in Two Significant Aqueous Ionic Liquid Solutions by Physicochemical and Computational Studies

To investigate the solution behavior of nicotinic acid (vitamin B₃) in two significant aqueous ionic liquid solutions, viz., BTEAC (benzyltriethylammonium chloride) and BTBAC (benzyltributylammonium chloride), we have studied some physicochemical parameters such as density, viscosity, surface tension, refractive index, and conductivity measurements at concentrations of 0.001, 0.003, and 0.005 mol·kg^–1, as well as at temperatures of 298.15, 303.15, 308.15, and 313.15 K under an atmospheric pressure of 1.013 bar. The limiting apparent molar volumes (φ_V⁰) derived from the Masson equation, the viscosity parameters, A- and B-coefficients, and molar refraction (R_M) from the Lorentz–Lorenz equation are used to criticize the solute–solute and solute–solvent interactions that prevail between vitamin B₃ with aqueous IL solutions. Transfer volumes (Vφ_tr⁰) and interaction parameters (V_AB, V_ABB) are also helpful for the determination of interactions associated with the ternary systems. Conductivity data is also used to explain the nature of interaction in the (vitamin B₃ + aq. ILs) mixtures. Several thermodynamic parameters, such as Δμ₁^0#, Δμ₂^0#, TΔS₂^0#, and ΔH₂^0#, show that there are substantial molecular interactions existing in the studied system. From ¹H NMR, ultraviolet–visible (UV–vis) spectroscopy information data also supported our experimental as well as theoretical findings. Optimization energy calculation by computational analysis using the density functional approach leads to the stability of the molecular assembly of the ternary (vitamin B₃ + IL + H₂O) system at the molecular level to validate the experimental results.