title: Imidazole facilitates electron transfer from organic reductants.
abstract: 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.
authors.affiliation: Department of Biological Sciences, Wayne State University, Detroit, MI 48202, USA.
authors.forename: Brian H
authors.initials: BH
authors.lastname: Kipp
authors.forename: Chadi
authors.initials: C
authors.lastname: Faraj
authors.forename: Guoliang
authors.initials: G
authors.lastname: Li
authors.forename: David
authors.initials: D
authors.lastname: Njus
mesh_terms: 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
chemical_list: D016227:Benzoquinones; D007093:Imidazoles; D011522:Protons; D019163:Reducing Agents; D014810:Vitamin E; D006859:Hydrogen; D001205:Ascorbic Acid