Identification of the photochemical decomposition product of chlorothalonil by 13C n.m.r. spectroscopy

The light-induced decomposition of chlorothalonil (2,4,5,6-tetrachloroisophthalonitrile) in benzene and toluene was found to give rise to one and three products respectively. These were shown by gas chromatography-mass spectrometry to be trichlorodicyanobiphenyls and the benzene adduct was fully identified by ¹³C n.m.r. spectroscopy as 2,4-dicyano-3,5,6-trichlorobiphenyl.