The cerous p-methoxybenzenesulfonate (I) and cerous p-toluenesulfonate (II) mediators were prepared and studied by electrochemical and kinetic methods. The reactivity of several alcohols, diols and arenes in the oxidation reaction with I and II was established, and electrochemical oxidation of some of them was carried out, leading to products with selectivity. The behaviour of these mediators is in agreement with the results of the experiments, and can be explained by the effects produced by the different ligands.