Quinones are expected to undergo two reversible, one electron reductions in aprotic solvents. Cyclic voltammograms (CV's) almost always show an oddly low current second  reduction and increased current between the two waves. Concentration dependence studies give evidence for a surface process because these oddities are more extreme at low concentration. The most likely surface chemistry is proton transfer from the phenolic groups on the glassy carbon surface to the doubly reduced quinones. Such a process would give a third, broad wave inbetween the other two. When naphthol was added to a relatively high concentration of quinone (~1mmol/L) during the CV experiments, the 2nd wave was replaced by a broad intermediate wave. The glassy carbon electrode was oxidized or reduced and the concentration study was repeated in each case. The presence of oxidized groups caused greater distortion of the CV's and the lack of them caused less distortion.

Unintentional proton coupled electron transfer as an explanation for the odd cyclic voltammetry behavior of quinones at glassy carbon electrodes in organic solvents

243rd National Meeting (2012)

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