Change in reaction pathway in the reduction of 3,5-di-tert-butyl-1,2-benzoquinone with increasing concentrations of 2,2,2-trifluoroethanol.
The electrochemical reduction of 3,5-di-tert-butyl-1,2-benzoquinone, 1, has been studied in acetonitrile with added 2,2,2-trifluoroethanol, 2. At low concentrations of 2 the reaction proceeds by the following pathway: reduction of the quinone (Q) to its anion radical (Q*-) followed by complexation of the anion radical with 2 (HA) and the further reduction of the hydrogen-bonded complex (Q*- (HA)) to form HQ- and A-. The latter reaction is a concerted proton and electron- transfer reaction (CPET). At higher concentrations of 2, the pathway changes. The first steps remain the same, but now Q*- (HA) is reduced to HQ- via a disproportionation reaction with Q*- along with proton transfer from HA to Q*- to form HQ* which is reduced to HQ-. The only mechanism that could be found which would account for all of the data involves proton transfer to Q*- occurring within a higher complex, Q*-(HA)3.
Macías-Ruvalcaba
Norma A
NA
Department of Chemistry, University of Arizona, Tucson, Arizona 85721, USA.
Okumura
Noriko
N
Evans
Dennis H
DH
D016227:Benzoquinones / Q000737:chemistry*; D004563:Electrochemistry; D010084:Oxidation-Reduction; D014270:Trifluoroethanol / Q000737:chemistry*
D016227:Benzoquinones; C054466:3,5-di-tert-butyl-1,2-benzoquinone; D014270:Trifluoroethanol