Photodechlorination of Aroclor 1254 (1000 mg/L) in an
alkaline 2-propanol solution at \lambda = 254 nm proceeded with a high quantum yield (\phi = 35.0) as determined by C1-
release. The Aroclor was completely dechlorinated in 30
min and gave predominantly biphenyl (BP). After 20 h
of solar irradiation, only partial dechlorination (25%) was
observed, and no BP was formed. In the presence of
phenothiazine (PT) sensitizer (5 mM) the Aroclor was
completely dechlorinated to BP in 1 h at 350 nm (\phi = 2.33) and in 4 h by exposure to sunlight. Under the same conditions, Aroclor 1254 extracts of contaminated soil (730
mg/L) were dechlorinated in 2 h at 350 nm (\phi = 0.28) and
in 20 h on exposure to sunlight. The photoreaction was
completely quenched by oxygen and nitrobenzene (0.1 M).
Moreover the Aroclor was thermally (ca. 80 "C) dechlorinated
to BP using di-tert-butyl peroxide. A free-radical chain reaction was suggested in which the aryl radical anion, Ar(*-)-Cl, was a key intermediate in the dechlorination process
