Temperature and concentration dependent physicochemical interactions of L-ascorbic acid in aqueous LiCl solution: Experimental and theoretical study

Abstract

Densities (ρ) and viscosities of vitamin L-ascorbic acid (LAA) in the presence of LiCl in aqueous media have been calculated over the temperature range 288.15–298.15 K. The values of densities increase with increases in concentrations of solute and co-solutes and decreases with temperature. The apparent molar volume (Vϕ), partial molar volume (Vϕ°) and viscosity B-Coefficient (B) have been calculated from the density data and further transfer parameters [partial transfer volume of (ΔtrVϕ°) and transfer values of B-Coefficient (ΔtrB)] for vitamin LAA have been calculated. The values of partial molar expensibilities and second order derivative have been deduced for the prediction of structure making and breaking nature of vitamin LAA in aqueous environment of LiCl. ∆S2o# and ∆H2o# are positive for LAA in co-solutes studied which advocate that the bond breaking and decrease in order is accompanied with the formation of the transition state. Further, DFT studied between LAA with [Li(H2O)n]+ have been performed to confirm the interactions as obtained from the experimental data.TD-DFT of the LAA in presence and absence of tetrahedrally hydrated lithium and chloride ions has been performed to find the excitation energy as well λmax. It is observed that maximum stabilization is achieved when lithium ions are tetrahedrally hydrated. Further effect of water as a solvent is studied on the most stable system. Further, the effect of temperature on the stability of the LAA along with tetrahedrally lithium and chloride ions at 398, 318 and 328 K has been investigated.