125076-48-4Relevant academic research and scientific papers
The Marcus theory of reactions of quinolinium ions with BH4- and OH-1
Kim, Duckhee,Lee, In-Sook Han,Kreevoy, Maurice M.
, p. 1889 - 1894 (2007/10/02)
The reactions of quinolinium ions with alkaline solutions of BH4- in a 4:1 mixture of 2-propanol and water were studied. Four 1-benzyl-3-cyanoquinolium ions and two 3-(aminocarbonyl)-1-benzylquinolinium ions were used. The quinolinium ions first reversibly add a nucleophile (mostly to the 4-position) and then are more slowly reduced to the 1,2- and 1,4-dihydroquinolines. The equilibrium constant for the addition of OH- or OR-, the rate constant for the addition, the rate constant for solvolysis of the adduct, and the rate constant for reaction of BH4- with the quinolinium ion were determined in each case. The quinolinium ion concentration was kept low enough so that only one of the hydridic hydrogens of BH4- was transferred to a quinolinium ion. Adduct formation and reduction by BH4- both have rates in the range 105-107 M-1 s-1, and the Br?nsted α values are similar. Both sets of rate constants can, roughly, be fitted by the Marcus theory of atom and group transfer if the intrinsic barrier is assumed to arise exclusively from the reorganization of the quinolinium ion. Since the presumptive critical complex for H- transfer between BH3 units, B2H7-, is a known, stable ion, it is reasonable that the reorganization of BH4- does not contribute significantly to the intrinsic barrier for its reactions. The Marcus theory, and related ideas, such as the Leffler-Hammond principle, apparently can be usefully applied to reactions quite different from the original model, but the exact values of the derived parameters quite possibly do not have their apparent physical significance.
Marcus Theory of a Perpendicular Effect on α for Hydride Transfer between NAD+ Analogues
Kreevoy, Maurice M.,Lee, In-Sook Han
, p. 2550 - 2553 (2007/10/02)
The Bronsted α (=d(lnkij)/d(lnKij)) for an atom- or group-transfer reaction depends on the location of the substitution and the tightness of the transition state (τ) as well as the resemblence of the transition state to reactants and products.Within Marcus theory, τ can be related to rates of symmetrical reactions.These ideas have been successfully applied to hydride transfer between NAD+ analogues.A series of 1-benzyl-3-cyanoquinolinium ions, substituted in the benzyl group, has been prepared.Rate and equilibrium constants have been determined for their reactions with 10-methylacridan.A Bronsted α of 0.37 has been obtained.From Marcus theory, using previously reported symmetrical exchange rate constants, the same value is calculated.This is displaced from 0.5 mainly by the looseness of the transition state, a perpendicular effect related to the partially hydridic character of the in-flight H.This H is estimated to have -0.23 electron of excess charge and a total bond order of 0.77 in the transition state.
