Reaction of NADH models with methylene blue
- 1 January 1985
- journal article
- research article
- Published by Wiley in Recueil des Travaux Chimiques des Pays-Bas
- Vol. 104 (5) , 131-138
- https://doi.org/10.1002/recl.19851040503
Abstract
The NADH models, (1R)‐1,4‐dihydronicotinamide and (1R)‐1,4‐dihydroquinoline‐3‐carboxamide (1‐4, R = X‐benzyl or octyl), are readily oxidized by methylene blue (MB⊕), yielding the corresponding pyridinium ions and leuco‐methylene blue (MBH). Under aerobic reaction conditions, molecular oxygen, present in the reaction solution, rapidly reoxidizes MBH to MB⊕, thereby allowing the study of the oxidation of the NADH models under pseudo‐first‐order reaction conditions. In order to elucidate the mechanism of the oxidation of the NADH models by MB⊕, the influence of the MB⊕ concentration, solvent and temperature has been studied as well as the effect of substituent variation in the benzyl group in a series of 1‐(X‐benzyl)‐1,4‐dihydronicotinamides (1a‐f). For one of the model compounds, 1‐benzyl‐1,4‐dihydronicotinamide (1a, BNAH), the primary and the secondary isotope effect and the temperature dependence of the kinetic isotope effect have been determined. It is concluded that oxidation of the NADH models by MB⊕ most likely proceeds by a rate‐determining hydride transfer process via a linear, symmetrical transition‐state structure.Keywords
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