Study On Structure And Property Of Protonated Pyridoxine

Vitamin B6 has a role in enzymatic reactions, and its antioxidant activity is strong, so it has attracted a lot of attention. In this thesis, the molecular structures, proton affinities, ionization potentials, and electron affinities for hydrogenated pyridoxine (PN) have been predicted by using a carefully selected theoretical approach B3LYP/DZP++ . The results reveal that the protons are favorable to attach to the nitrogen of PN. Attaching protons to other sites of PN are in energy higher than that of nitrogen site by 27.0～56.1 kcal/mol. The proton affinities of PN (protonation at N1) are predicted to be 232.3 kcal/mol. For (PN+H)·(these radical come from electron attachment to the corresponding protonated (PN+H)+ cations), the lowest-energy structure is unchanged compared to (PN+H)+. The theoretical ionization potential is 4.94 eV. For (PN+H)? (these anions come from electron attachment to the corresponding (PN+H)·radical), the energetic order of the anions differs significantly from that of the analogous radicals and cations. Among of these, the most stable isomers are the a3 and the second most stable structures are the a4, which are only higher than the a3 by 0.4 kcal/mol in energy. Three kinds of neutral-anion energy separations reported in this thesis are the theoretical adiabatic electron affinities (AEA), vertical electron affinities (VEA), and vertical detachment energies (VDE). Taking into account the solvent effect, protonation of PN in aqueous solution is more stable and neutral hydrogenated PN more readily takes up solvated electrons.In addition, Vitamin C is also investigated with B3LYP/DZP++ scheme. Several possible isomers and electron affinities are presented.