On the mechanism of quenching of singlet oxygen by chlorinated phenolic pesticides

Abstract
Reaction of polychlorophenols with photophysically generated singlet oxygen was carried out in solvents of different polarity. Rate constants for total removal of singlet oxygen go from 5 × 107 M–1 s–1 in benzene‐methanol mixtures to 2 × 109 M–1 s–1 in water. From substituent and solvent effects it can be concluded that a charge transfer mechanism operates in the photo‐oxygenation. Although physical quenching of singlet oxygen is the main deactivating process, chemical reaction constitutes a considerable contribution. A detailed kinetic study was made, and from the data, photo‐oxidation via singlet oxygen of industrial wastes containing polychlorophenols, appears as a reliable possibility.