Accurate Standard Hydrogen Electrode Potential and Applications to the Redox Potentials of Vitamin C and NAD/NADH

• Published in: The journal of physical chemistry. A, Molecules, spectroscopy, kinetics, environment, & general theory Vol. 119; no. 2; pp. 369 - 376
• Main Authors: Matsui, Toru, Kitagawa, Yasutaka, Okumura, Mitsutaka, Shigeta, Yasuteru
• Format: Journal Article
• Language: English
• Published: United States American Chemical Society 15.01.2015
• Subjects: Affinity; Ascorbic Acid - chemistry; Computation; Computer Simulation; Electrode potentials; Electrodes; Electrons; Hydrogen - chemistry; Mathematical models; Models, Chemical; Molecular Structure; NAD - chemistry; Nicotinamide adenine dinucleotide; Oxidation-Reduction; Protons; Vitamin C; Water - chemistry
• ISSN: 1089-5639; 1520-5215
• DOI: 10.1021/jp508308y

We computationally evaluated the standard hydrogen electrode (SHE) potential in aqueous phase and the Gibbs energy of a proton from the experimental pK a values of alcohol molecules. From the “golden standard” CCSD(T)/aug-cc-pVTZ level calculation, we estimated the SHE potential as 4.48 V, which is very close to the IUPAC-recommended experimental value of 4.44 V. As applications to the Gaussian-3 (G3) methods, which also reproduce the “golden standard” level calculations, we computed various pK a values and redox potentials for a vitamin series. For vitamin C, we support the experimental result of +0.35 V and predict the pK a value of d-ascorbic acid to be 3.7–3.9. Using a model molecule for nicotinamide adenine dinucleotide (NAD), we reproduced the redox potential and determined the order of the proton/electron addition, based on both the proton affinity and redox potential.