The potentiostatic reduction of Cu(II) in HCl solutions saturated by O-2 was investigated to determine the competition of redox reactions between Cu(I), O-2, and Cl-. Cu(I) reacts with O-2 to form OH radicals, which in turn oxidize Cl- to Cl radicals. When the radical scavenger toluene is added to the electrolytic environment, benzaldehyde and benzylchloride are obtained. In Fe(III)/Na4P2O7 solutions saturated by O-2, OH radicals are produced by the reaction between electrogenerated reagents Fe(II) and H2O2. In the presence of toluene, cresols are the main products, largely prevailing over benzaldehyde. The parameters determining the distribution of such products were also investigated.