The FeCl4(-) ion, heterogenized on a Dowex ion exchange resin, catalyzes the aerobic photodecomposition of neat CH2Cl2. Phosgene production was used to characterize the extent of decomposition, although it appears to be a secondary product from the decomposition of chloroform, which is suggested to arise from the reaction of dichloromethanol with hydrogen chloride. The yield of CHCl3 increases when the production of phosgene is suppressed by water or acetonitrile. CuCl4(2-), likewise heterogenized on Dowex, is photocatalytically inactive.
Heterogenized on a polystyrene anion exchange resin and in the presence of oxygen, CuCl 2À 4 catalyzes the photodecomposition of chloroform at wavelengths above 345 nm with greater efficiency than an equivalent amount in homogeneous solution. The reaction is proposed to proceed in two stages, the first stage yielding CCl 4 and HO À 2 as products, the second consisting of a chain reaction resulting from the CuCl 2À 4 -catalyzed photodissociation of CCl 4 , yielding phosgene with CCl 3 radicals as chain carriers. Photodecomposition is retarded by added Cl À , CH 3 CN, C 6 H 12 or C 2 H 5 OH, which is ascribed to the displacement of CHCl 3 molecules from the vicinity of the copper by attraction to the polystyrene matrix or to the alkylammonium cation sites.
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