Free radical/singlet dioxygen system under the conditions of catalytic hydrogen peroxide decomposition

Hydrogen peroxide decomposition and the oxidation of unsaturated compounds (anthracenes, alkenes, etc.) in the H2O2/(VAcOH)-Ac-(V) system occur via a molecular mechanism. H2O2 decomposes to yield singlet dioxygen O-1(2)((1)De lta(g)) Among V(V) peroxo complexes of different compositions, coordinated superoxide radical anions V-(V)(O-2(radical anion)) are found in a steady-s tate concentration in the system under investigation. Styrene oxidation in the H2O2/(VAcOH)-Ac-(V) system unusually accelerates in the presence of 2,6 -di-tert-butyl-4-methylphenol (BHT), which is an inhibitor of radical chain reactions. This is explained by a decrease in the V(V)(O-2(radical anion)) concentration and an increase in the concentration of dissolved O-1(2) in the presence of ionol. A new phenomenon in the chemistry of singlet dioxyge n is found: the ESR signal from the paramagnetic system upon its interactio n with O-1(2) broadens in an unusually drastic manner (up to 10 G). This br oadening is virtually independent of the nature of the radicals, the acidit y of the medium, and the nature of the metal catalysts used for the generat ion of O-1(2)((1)Delta(g)).