ELECTROREDUCTION OF DIALKYL PEROXIDES - ACTIVATION-DRIVING FORCE RELATIONSHIPS AND BOND-DISSOCIATION FREE-ENERGIES

The electrochemical reduction of five dialkyl peroxides in DMF was stu died by cyclic voltammetry. The electron transfer (ET) to the selected compounds is concerted with the oxygen-oxygen bond cleavage (dissocia tive ET) and is independent of the electrode material. Such an electro chemical behavior provided the opportunity to study dissociative ETs b y using the mercury electrode and therefore to test the dissociative E T theory by using heterogeneous activation-driving force relationships . The convolution voltammetry analysis coupled to the double-layer cor rection led to reasonable estimates of the standard potential (E degre es) for the dissociative ET to dialkyl peroxides, as supported, whenev er possible, by independent estimates. A thermochemical cycle based on the dissociative ET concept was employed to calculate the bond dissoc iation free energies (BDFEs) of the five peroxides, using the above E degrees s together with electrochemical or thermochemical data pertain ing to the redox properties of the leaving alkoxide ion. The BDFEs wer e found to be in the 25-32 kcal/mol range, suggesting a small substitu ent effect. The dissociative ET E degrees s were also used together wi th the experimental quadratic free energy relationships to estimate th e heterogeneous reorganization energies.