Investigation of intermolecular interactions of l-Valine and l-Phenylalanine with muscle relaxant drug mephenesin molecule prevalent in aqueous solution by various physico-chemical methods at T=298.15K-313.15K.

A complete chemical analysis of significant intermolecular interactions of l-Valine (L-Val) and l-Phenylalanine (L-Phe) with Mephenesin (MEPN) molecules in aqueous solution has been studied by different physicochemical methodologies at various temperatures ( = 298.15 K-313.15 K at an interval of 5 K) and concentrations (0.001 mol kg, 0.003 mol kg, 0.005 mol kg) of aqueous MEPN solution. The limiting apparent molar volume () and experimental slope () values are found from the equation of Masson, viscosity and -coefficient determined using the equation of Jones-Doles, molar refraction () and limiting molar refraction () derived by the Lorentz-Lorenz equation, express that in our experimental solution of amino acids (AAs) in aqueous MEPN, the solute-solvent interaction predominates over the solute-solute and solvent-solvent interactions for these ternary solutions. These are also justified by the measurement of various thermodynamic parameters, free energy of activation of viscous flow per mole of solvent() and solute (), activation of viscous flow of enthalpies () and entropies () The characteristics of structure-breaking of solutes in the aqueous drug solution have been identified by Hepler's method and value. The spectroscopic methods like UV-visible and proton-NMR studies help to explicate the strong AA-MEPN interactions in the solution phase and obtain a good correlation with theoretical studies. Theoretical investigations are checked to authenticate the experimental observations and according to both studies, L-Phe-MEPN interaction is greater than L-Val-MEPN interaction. The experimental and correlated research data are useful for the development of model combinations of AAs with drug molecules in pharmaceutical and medicinal chemistry.