The Measurements of Acid Dissociation Constant and Thermodynamic Properties of Betanin in aqueous solution at different Temperatures

In this research work, the values of the acid dissociation constant (pKa1, pKa2, pKa3, and pKa4),the optimized structure, and the thermodynamic properties of betanin were calculated in aqueoussolution at various temperatures by ab initio and DFT methods. Density function theory (DFT)has been used based on B3LYP/6-31+G(d) theory to explain the obtained acid dissociationconstants of betanin and also interactions between solvent and solvated cation, anion, and neutralspecies of betanin. Thomasi s method was used to analyze the formation of intermolecularhydrogen bonding between the water molecule and various species of betanin. In addition,thermodynamic parameters of ΔH, ΔG, and ΔS were obtained for dissociation reactions ofbetanin. Results indicates that in deprotonation process of GLY-ASP, pKa1, pKa2 and pKa3increases by temperature increasing and also, pKa4 decrease by temperature growth.

Keywords:

Optimized Structure , Betanin , Thermodynamic Properties , ab initio , DFT Method