DECOMPOSITION OF HYDROGEN-PEROXIDE CATALYZED BY VANADIUM(V) COMPOUNDS- THE PATHWAYS FOR THE FORMATION OF OZONE

Reactions of H2O2 in trifluoroacetic acid catalyzed by vanadium(v) com pounds were studied. The system under study exhibits unusual behavior: along with oxygen, large quantitaties (10-15 %) of ozone are found in the products of hydrogen peroxide decomposition; difficultly oxidizab le compounds (alkanes, arenes, and perfluoroalkenes) are oxidized unde r mild conditions. The rates of the oxidation of individual substrates are commensurable. However, when two compounds are simultaneously pre sent in the reaction mixture, cyclohexane stops the oxidation of all o f the other substrates, arenes suppress the oxidation of perfluoroolef ins, and perfluoro-1-octene stops the consumption of internal perfluor oolefins. The effect of the oxidizable substrates on the amount of ozo ne evolved was studied. Based on the kinetic data obtained, a mechanis m that involves the consecutive formation of several active complexes of vanadium(v) responsible for the oxidation of substrates and for the formation of ozone is suggested. In terms of the scheme suggested, th e inner-sphere oxidation of the peroxo ligand by the coordinated perox otrifluoroacetic acid affords a complex incorporating O-3(2-) as a lig and. The latter acts as the precursor of the ozone. A mathematical mod el that adequately describes the experimental data is proposed.