Hydration of species derived from ascorbic acid in aqueous solution. An experimental and theoretical study by using DFT calculations

Abstract

B3LYP/6-31G* calculations have been carried out in order to study the theoretical structures of the following forms of ascorbic acid: unoxidized H2A, HA− and A2− anions, oxidized A and dimeric A2 forms as well in gas as in aqueous solution phases in order to observe the change carried out on the structural and vibrational properties in aqueous media. Therefore, the sodium ascorbate was characterized by infrared and Raman spectroscopy in solid and aqueous solution phases. Optimized geometries and relative stabilities for those species derived from ascorbic acid have been calculated taking the solvent effects into account by using the self-consistent reaction field theory. The role of specific and bulk contributions of solvent effect on the observable properties of the different species is clarified. The theoretical results are confronted with available experimental data. Good agreement between theoretical and available experimental results of harmonic vibration frequencies is found. The vibrational spectra of the A2− and A species were predicted. Significant effects on the parameters geometrical and vibrational frequencies are found for the studied species. In addition, the dipole moment, molar volume, solvation energies and force constants of the studied species are shown and discussed.