The Ce(IV) ions had been found to be very effective and selective one-electron oxidizing agent of numerous organic compounds. In our research group we have studied for many years the mechanisms of the oxidation reactions of phenol and aniline derivatives in acidic medium. These reactions in most cases occur through the step of complex cerium ions - organic compound formation (mainly 1:1) which disintegrate with internal electron transfer.

The oxidation of phenols leads to the formation of benzenoquinoes, diphenoquinones (strong  π-acceptors) and oligomeric compounds as the final products.

In case of the oxidation process of anilines the final products are dimeric N-phenyl-1,4-phenylene-diimines, diphenoquinone-4,4’-diimines, benzoquinones and oligomeric compounds. The crucial role in a type and constitution of obtained products have to play: (i) the acidic properties of oxidized phenol derivatives and of the cation radical rising in a first step; (ii) the electron densities of C4 carbon atoms and oxygen atoms; (iii) the acidity of the reaction medium, (iv) the steric hindrance, and (v) the nature of the process (heterogenic or homogenic).

Another interesting problem we have investigated is the oxidative cross-coupling of some 2,6- and N,N-disubstituted aniline derivatives with 4-aminophenol mediated by cerium(IV) ions in acidic media. We have proposed mechanism of this process occurring through the formation of indoaniline derivatives as the intermediate products.

The oxidative coupling of some 2,6-disubstituted phenol derivatives mediated by Ce(IV) ions in aqueous or aqueous-acetonitrile solutions of perchloric acid as well as in two-phase systems leads to the corresponding 1,4-benzoquinones, 4,4`-diphenoquinones and oligomeric poly(1,4-phenylene)oxides. These processes were discussed in terms of stabilities, pK values and electron densities at carbon C4, and oxygen atoms.

In recent years we have investigated the immobilization of cerium(III) ions (as a redox mediator) on a glassy carbon and platinum for electrooxidation reactions. The Ce(III) ions have been immobilized in Nafion^® films coated on the electrode surface. The redox activity of Ce(IV)/Ce(III) couple was characterized by cyclic voltammetry and aqueous acidic solutions. The cerium(III) ions immobilized Nafion films showed a mediation activity for the electrochemical oxidation of some substituted 1,4-hydroquinones, 4-aminophenols, 1,4-phenylene-diamines and 4-hydroxybenzoic acids. We have found that the cerium(III) ions reveal mediation activity and the modified electrodes have catalytic properties.