ABSTRACT
The free radical Gomberg-type biaryl synthesis using isoamyl nitrite was employed for the preparation of a number of tetra-, penta-, and hexa-chlorobiphenyls. Carbon-14 labeled 2,2',3,3',4,4',5,6'-octaehlorobiphenyl and 2,2',4,4',5,5'-hexa-chlorobiphenyl has been prepared via nitration of chlorobiphenyls of lower chlorine content and direct replacement of the nitro group by chlorine using carbon tetrachloride at elevated temperatures. A number of tetrachlorobiphenyls have been irradiated in hexane and methanol at 300 nm. Isomerization and formation of polymeric products was observed on irradiating several chlorobiphenyls in perfluorinated hydrocarbons. Similar reaction products were found after irradiation of chlorobiphenyls as thin films. Under these conditions, however, chlorobiphenyls with increased chlorine content were also observed. Gas phase irradiations of 2,2'-dichlorobiphenyl and 2,2',4,4',6,6'-hexachlorobiphenyl gave polymeric products. The products of the irradiation are biphenyl and acetone and similarities in mechanism of the irradiation with 60Co and a low pressure mercury lamp have been noted.
