CHEMICAL AND ELECTROCHEMICAL OXIDATION OF PHENOTHIAZINE

The oxidation of phenothiazine in dilute solutions of sulphuric acid l eads to the corresponding cation radical. Using a potentiometric techn ique, a pK(a) value of 5.72 +/- 0.05 was determined for phenothiazine. The kinetics has been studied and participation of both protonated an d unprotonated oxidant in the oxidation reaction has been confirmed. U sing a voltammetric technique with a rotating disk electrode, the anod ic oxidation of phenothiazine was shown to be a one-electron diffusion -controlled process. A quantum chemical explanation was found for the direction of phenothiazine protonation and the absence of a dimerizati on stage of oxidation.