837-43-4Relevant academic research and scientific papers
Hydride Transfer and Oxyanion Addition Equilibria of NAD+ Analogues
Ostovic, Drazen,Lee, In-Sook Han,Roberts, Roger M. G.,Kreevoy, Maurice M.
, p. 4206 - 4211 (1985)
Equilibrium constants, K, have been determined for the reduction of 10-methylacridinium ion by 15 N-heterocyclic hydride donors: acridine, quinoline, pyridine, and phenanthridine derivatives.The solvent was a mixture of 2-propanol and water in the ratio 4 : 1 by volume.Reduction potentials have been estimated for the corresponding cations in aqueous solution by assuming that the K's would be the same and accepting -361 mV as the reduction potential of the 3-(aminocarbonyl)-1-benzylpyridinium ion.These reduction potentials span 430 mV.Values of pKR have also been determined for six of the cations in the same solvent.For derivatives of the same ring system, -ΔlogK is approximately equal to ΔpKR, but a 4 log unit discrepancy appears when phenanthridine derivatives are compared with the 9-methylacridinium ion.
The role of homolytic bond dissociation energy in the deprotonation of cation radicals. Examples in the NADH analogues series
Anne, Agnès,Fraoua, Sylvie,Grass, Valérie,Moiroux, Jacques,Savéant, Jean-Michel
, p. 2951 - 2958 (1998)
The deprotonation of the cation radical of 9-cyanomethylacridane by a series of normal bases is investigated and its pK(a) and homolytic bond dissociation energy determined experimentally. The latter parameter has the largest value in the NADH analogue series, thanks to the strong destabilization of the corresponding cation by the cyano group. It thus allows a significant extension of the attempted correlation between the intrinsic barriers and homolytic bond dissociation energies (D). Aside from members of the series where bulky substituents cause a decelerating steric effect, the correlation is close to a proportionality to D/4. The same correlation applies for all the other cation radicals where the rate constants of deprotonation by normal bases are available. The respective contributions of the homolytic and ionic states in the dissociation of the two types of acid, cation radicals and the conjugate acid of the normal base, are such that a simple model can be developed which regards the deprotonation reaction as a concerted H atom/one-electron transfer. It explains why, for each cation radical, the deprotonation by normal bases gives rise to a single Bronsted plot and why the intrinsic barriers are proportional to D/4. In the NADH analogue series, the deviations from proportionality observed with bulky substituents, and to a lesser extent, upon changing the extent of charge delocalization over the cation radical molecule are accounted for by product and reactant work terms, respectively.
