Thermodynamic characteristics of NADH/NAD⁺ analogues in acetonitrile: 2-methyl, 4-methyl and 2,4-dimethyl 1-benzyl-dihydronicotinamides and the corresponding pyridinium species

Abstract

Procedures were elaborated for the syntheses of the title compounds. The thermodynamic changes brought about by each methyl substitution were then determined quantitatively. In acetonitrile, the respective one-electron oxidation and one-electron reduction potentials of the NADH and NAD' analogues were obtained by means of direct and indirect (using ferrocene mediators) cyclic voltammetry. ' The redox potentials of formal hydride transfers were deduced from the studies of equilibrated reactions occurring between the analogues. The pKa's of the cation radicals ensued.Key words: NADHRVAD' methylated analogues, one-electron transfers, hydride transfer, thermodynamics. Resum6: On a mis au point des mCthodes de synthkse des composCs mentionnCs dans le titre. On a ensuite determine quantitativement les changements thermodynamiques provoques par chaque substitution par un groupe mCthyle. Faisant appel i la voltampCromCtrie cyclique directe et indirecte ( i l'aide de mkdiateurs ferrockne), on a determine les potentiels respectifs de l'oxydation i un electron et de la reduction par un Clectron des analogues de NADH et NAD' dans I'acCtonitrile. Les potentiels rCdox des transferts formels d'hydrure ont it6 dCduits des Ctudes sur des rCactions CquilibrCes se produisant entre les analogues. Les pKa des radicaux cations en dCcoulent.

Thermochemistry of Proton-Coupled Electron Transfer Reagents and its Implications

“…359 Methylated BNAH derivatives show thermochemistry that is similar to the parent compound in MeCN. 360…”

Hydricities of BzNADH, C5H5Mo(PMe3)(CO)2H, and C5Me5Mo(PMe3)(CO)2H in Acetonitrile

“… a Value calculated from the Δ G H − value for BzNADH and from equilibrium data given in refs and for hydride transfer reactions between BzNADH and the respective NAD + model compounds. …”

“…The relative thermodynamic hydricities of NADH model compounds have been studied using equilibrium studies of hydride transfer reactions. − Efforts to determine the hydride donor abilities of these compounds on an absolute scale have also been described. Such absolute values would allow comparisons with other classes of hydride donors.…”

Electrochemistry of Electron Transfer Probes. Observation of the Transition from Activation to Counterdiffusion Control in the Fragmentation of α-Aryloxyacetophenone Radical Anions1a

“…The lack of directly measured thermochemical properties have in a few cases been circumvented by constructing thermochemical cycles in which most of the terms are thermochemical properties of closed shell compounds. 19 Examples include the estimation of pK a values of radical cations, [20][21][22][23] basicity of radical anions, 24 and cleavage of radical anions 13,25,26 and radical cations. 26,27 J.…”