Primary Kinetic Isotope Effects on Hydride Transfer from 1,3-Dimethyl-2-phenylbenzimidazoline to NAD+ Analogues

Autor:	Eunhee Jeoung, In-Sook Han Lee, Maurice M. Kreevoy
Rok vydání:	2001
Předmět:	Chemistry Hydride Triatomic molecule General Chemistry Photochemistry Biochemistry Bond order Catalysis Marcus theory chemistry.chemical_compound Colloid and Surface Chemistry Atom Kinetic isotope effect Physical chemistry Pyridinium Equilibrium constant
Zdroj:	Journal of the American Chemical Society. 123:7492-7496
ISSN:	1520-5126 0002-7863
DOI:	10.1021/ja004232+
Popis:	Primary kinetic isotope effects (KIE) have been determined spectrophotometrically for the reaction of NAD+ analogues (pyridinium, quinolinium, phenanthridinium, and acridinium ions) with 1,3-dimethyl-2-phenylbenzimidazoline in a 4:1 mixture of 2-propanol and water by volume at 25 °C. The values of KIE varied systematically from 6.27 to 4.06 as the equilibrium constant changed from around 10 to around 1012. This is consistent with Marcus theory of atom transfer, assuming that there are no high-energy intermediates. Within this theory, the perpendicular effect is responsible for most of the change in KIE. The Marcus theory of atom transfer is consistent with a linear, triatomic model of the reaction. Perpendicular effects arise from the systematic decrease of bond distances and increase of bond orders in the critical complexes of the two related degenerate hydride transfer reactions as their C−H bonds become stronger. The parallel effect (Leffler−Hammond effect) is attenuated by the fairly high intrinsic ba...
Databáze:	OpenAIRE
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