Mechanism of electrohydrodimerization of 2-cyclohexen-1-one on mercury from aqueous solutions. Part 2.—Results obtained for solutions containing triton X-100

Abstract

The effect of Triton X-100 additions upon waves I and II for 2-cyclohexen-1-one (R) electroreduction on mercury from aqueous solutions has been investigated. The presence of Triton X-100, while allowing the electron transfer to remain Nernstian, affects the electrode reaction mechanism whenever the latter involves adsorbed reaction partners or else a protonation prior to or during the rate-determining step. In both cases the effect of Triton X-100 is mainly due to the fact that it displaces reaction partners from direct contact with the electrode surface. In the case of protonation, adsorbed water molecules are also regarded as reaction partners, in that they are much stronger proton donors than non-adsorbed ones. The effect of Triton X-100 is particularly remarkable on wave II for 6 < pH < 10. Here a gradual increase in Triton X-100 concentration shifts the rate control from the coupling step (2RH ˙→ R₂H₂) to the preceding protonation step (R ˙^–+ HA ⇌ RH ˙+ A^–) of the radical anion R ˙^–.