Journal of the American Chemical Society

Methylcobalamin's Full-vs. Half-Strength Cobalt-Carbon sigma Bonds and Bond Dissociation Enthalpies: A> 10^ 15 Co-CH3 Homolysis Rate Enhancement following …

BD Martin, RG Finke

Index: Martin, Bruce D.; Finke, Richard G. Journal of the American Chemical Society, 1992 , vol. 114, # 2 p. 585 - 592

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Citation Number: 101

Abstract

Abstract: Methylcobalamin (MeCbl, MeB12) thermolyzed in ethylene glycol from 120 to 141 OC with 2, 2, 6, 6-tetramethylpiperidinyl-1-oxy (TEMPO) as a Me'trap gives the homolysis products Co1IBIzr and TEMPO-Me quantitatively. The 5, 6-dimethylbenzimidazole axial- base-off-base-on equilibrium in ethylene glycol has an enthalpy change of-5.1 (f 2) kcal mol- 'and an entropy change of-10.5 (f 4) cal mol-'K-', equilibrating between the 5, 6- ...