Products and Intermediates Formed During the Biacetyl-sensitised Photo-oxidation of Some Azo Dyes

The flash irradiation for a few microseconds of aqueous aerobic colutions of biacetyl (2,3-butanedione) and a number of different o-arylazonaphthols resulted in the formation of the corresponding diazonium ions and alpha-naphthoquinones. This was verified from the intermediate spectra obtained after the flash. Verification for the formation of diazonium ions was also obtained from flow experiments, in which the diazonium ion was identified by coupling it to H-acid, forming a new azo compound. Less than equimolar formation of the diazonium ion from one of the azo dyes investigated indicated the occurrence of side reactions in which diazenyl radicals could play a role