Photoreaction of Monochlorobenzene under Ultraviolet Irradiation

The photolysis of monochlorobenzene by ultraviolet irradiation was investigated and found to yield monochlorinated biphenyls, biphenyl, and benzene. The amounts of these products increased with reaction time up to 20 hours. The yields of 2-, 3- and 4-chlorobiphenyl, biphenyl and benzene in monochlorobenzene were 708 ppm, 965 ppm, 1012 ppm, 226 ppm and 410 ppm, respectively, after 20 hours, but subsequent increases were relatively slow. One possibility is that monochlorinated biphenyls formed from monochlorobenzene are gradually decomposed by further irradiation. The photostability of monochlorinated biphenyls and biphenyl was in the order : biphenyl »4-chlorobiphenyl>3-chlorobiphenyl>2-chlorobiphenyl.