Comportement electrochimique d'oxocarbones et d'aci-reductones en relation avec le transport d'electrons dans les processus biologiques—VII. Reduction de l'acide rhodizonique en milieu aqueux acide

The hypothesis of an ECE1 mechanism may justify the electrochemical behavior observed for the reduction of dihydrated rhodizonic acid. In a first step, RDZ, 2H₂O is irreversibly reduced via a two-electron process without preceding dehydration. The following chemical step is an acid-catalysed dehydration of the monohydrated intermediate species and produces 1,4-tetrahydroxybenzoquinone (THQ) which is reduced via a two-electron process at a potential less negative than RDZ, 2H₂O. According to the hypothesis of an ECE1 mechanism a value of k = k′ (H⁺) with k′ = 145 ± 7 s^?1 is found for the rate constant of the chemical step. The monohydrated intermediate species is reducible via a two-electron process, and without preceding dehydration, at a potential more negative than RDZ, 2H₂O.