Imidazole facilitates electron transfer from organic reductants.
In cyclic voltammetry studies at pH 8, imidazole facilitates oxidation of organic compounds that normally lose hydrogen atoms. High concentrations of imidazole shift the oxidizing wave of ascorbic acid, 2,3-dimethoxy-5-methyl-1,4-hydroquinone, and the vitamin E analogue Trolox toward lower potentials. By contrast, imidazole has no effect on the cyclic voltammogram of methyl viologen, which undergoes electron rather than hydrogen-atom transfer. The effect of imidazole is observed at pH 8.0 but only to a lesser extent at pH 5.5 indicating that imidazole must be unprotonated to facilitate oxidation. Digital simulation shows that these results are consistent with a mechanism in which imidazole acts as a proton acceptor permitting concerted proton/electron transfer by the organic reductant.
Kipp
Brian H
BH
Department of Biological Sciences, Wayne State University, Detroit, MI 48202, USA.
Faraj
Chadi
C
Li
Guoliang
G
Njus
David
D
D001205:Ascorbic Acid / Q000737:chemistry / Q000378:metabolism; D016227:Benzoquinones / Q000737:chemistry / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D004579:Electron Transport; D006859:Hydrogen; D006863:Hydrogen-Ion Concentration; D007093:Imidazoles / Q000737:chemistry*; D010084:Oxidation-Reduction; D011199:Potentiometry; D011522:Protons; D019163:Reducing Agents / Q000737:chemistry*; D014810:Vitamin E / Q000031:analogs & derivatives / Q000378:metabolism
D016227:Benzoquinones; D007093:Imidazoles; D011522:Protons; D019163:Reducing Agents; D014810:Vitamin E; D006859:Hydrogen; D001205:Ascorbic Acid