First Estimation of C₄−H Bond Dissociation Energies of NADH and Its Radical Cation in Aqueous Solution

Abstract

The heterolytic and homolytic C4-H bond dissociation energies of NADH and its radical cation (NADH*+) in aqueous solution were estimated according to the reaction of NADH with N,N,N',N'-tetramethyl-p-phenylenediamine radical cation perchlorate (TMPA*+) in aqueous solution. The results show that the values of the heterolytic and homolytic C4-H bond dissociation energies of NADH in aqueous solution are 53.6 and 79.3 kcal/mol, respectively; the values of the heterolytic and homolytic C4-H bond dissociation energies of NADH*+*+ in aqueous solution are 5.1 and 36.3 kcal/mol, respectively, which, to our knowledge, is first reported. This energetic information disclosed in the present work should be believed to furnish hints to the understanding of the mechanisms for the redox interconversions of coenzyme couple NADH/NAD+ in vivo.

Thermochemistry of Proton-Coupled Electron Transfer Reagents and its Implications

“…Nicotinamide radical cations are quite acidic, like the hydrocarbon radical cations discussed above, and the closed shell (reduced) nicotinamides are very poor acids, highlighting the typical preference of these compounds to undergo PCET rather than ET or PT. Cheng et al have presented thermochemical data for aqueous NADH351 and for 10-methyl-9,10-dihydroacridine (AcrH 2 ) in DMSO352 and MeCN (Figure 9),353 although questions have been raised about some of these results 354. For AcrH 2 in MeCN, there is reasonable agreement between Cheng’s values and those reported earlier by Savéant and Neta, but there is a substantial disagreement in the values for BNAH 355.…”

Size‐ and Shape‐Dependent Activity of Metal Nanoparticles as Hydrogen‐Evolution Catalysts: Mechanistic Insights into Photocatalytic Hydrogen Evolution

“…[15] The ET state is capable of oxidizing NADH (E ox = 0.76 V vs. SCE) [33,34] by the MesC + moiety in AcrCMesC + (E red = 1.88 V vs. SCE) [15] to produce NADHC + and AcrC-Mes (Scheme 1). [17] The resulting NADHC + undergoes facile deprotonation to produce NADC that can reduce Acr + -Mes by ET from NADC to produce additional AcrC-Mes.…”

Detection of a Radical Cation of an NADH Analogue in Two‐Electron Reduction of a Protonated p‐Quinone Derivative by an NADH Analogue

“…[24] The one-electron oxidation potential of NADH (E ox = 0.76 V vs SCE) [6,25] in aqueous solution is close to that of AcrH 2 (E ox = 0.81 V vs SCE) [6,25] [28] The E red value of TolSQ in the presence of HClO 4 was determined by second-harmonic alternating-current voltammetry (SHACV) because of the instability of TolSQHC ( Figure S2). …”