Polarographic behaviour of p-diacetylbenzene ; an example of a compound with two electroactive centers

p-Diacetylbenzene is reduced at pH 2–5 in the diprotonised form in a reversible two-electron step to a bi-radical with a half-life of the order of seconds. Reversibility was confirmed by single-sweep and commutator methods. At pH-values below 2 the reversibility is perturbed by transformation of the bi-radical into p-(1-hydroxyethyl)acetophenone in an acid-catalysed reaction. The same product results also at pH-values above 5, where the reversibility is affected either by a base-catalysed deactivation of the bi-radical or by the formation of a monoprotonated form, reduced irreversibly in two successive steps.