ACETONE-INDUCED PHOTODECHLORINATION OF AROCLOR 1254 IN ALKALINE 2-PROPANOL - PROBING THE MECHANISM BY THERMOLYSIS IN THE PRESENCE OF DI-TERT-BUTYL PEROXIDE

Aroclor 1254 (1860 mg/l) in alkaline 2-propanol and in the presence of acetone (4% v/v) was photodechlorinated to biphenyl at lambda > 300 nm with exceptionally high quantum yield (PHI = 18). Under similar conditions photodechlorination of extracts of Aroclor 1254 contaminated soil (730 mg/kg) proceeded with lower quantum yield-PHI = 0.4. While oxygen severely quenched photolysis, dechlorination was accomplished under thermal conditions using di-t-butyl peroxide, t-BuOOBu-t, as free radical initiator. A free radical chain reaction is suggested in which acetone triplet, T1(n,pi*), or t-BuO. radical abstracts H-atom from 2-propanol to give the ketyl radical, (CH3)2COH, which after losing a proton to the alkaline medium gives the ketyl radical anion, (CH3)2CHO.-. The Aroclor in turn reacts with the latter species through an electron-transfer process giving unstable aryl radical anion, Ar-Cl.-, which cleaves releasing the chloride anion, Cl- and the aryl radical, Ar.