Quantum chemical study of the autoxidation of ascorbate |
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| Authors: | Nils Herrmann Norah Heinz Michael Dolg Xiaoyan Cao |
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| Affiliation: | Department of Chemistry, Institute for Theoretical Chemistry, University of Cologne, Cologne, Germany |
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| Abstract: | Reactions involved in the autoxidation of ascorbate have been investigated with quantum chemical first‐principles and ab initio methods. Reaction energies and Gibbs energies of the reactions were calculated at the density functional theory level applying the gradient‐corrected BP86 and the hybrid B3LYP functionals together with def2‐TZVP basis sets. Results of single‐point CC2, CCSD, and CCSD(T) calculations were used for calibration of the density functional theory data and show excellent agreement with the B3LYP values. Based on the Gibbs energy ascorbic acid AscH2 is found to be the energetically lowest species in aqueous solution, whereas the monoanion ascorbate AscH  is the most abundant one near pH = 7. Asc  was found to be the preferred reducing agent for autoxidation and oxidation processes. The results also support a metal‐catalyzed synthesis of the reactive oxygen species H2O2 according to a redox cycling mechanism proposed in literature. © 2016 Wiley Periodicals, Inc. |
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| Keywords: | ascorbic acid ascorbate autoxidation density functional theory coupled cluster theory texaphyrin ionization potential electron affinity motexafin gadolinium |
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