Photobenzidine Rearrangements. 7. Disproportionation and Recombination of N-Methylarylamino Radicals in the Photodecomposition of 1,4-Bis(p-cyanophenyl)-1,4-dimethyl-2-tetrazene and Other 2-Tetrazenes

Article abstract of DOI:10.1021/jo00336a014

The photochemical decomposition of 1,4-bis(p-cyanophenyl)-1,4-dimethyl-2-tetrazene (1c) in 1,2-dimethoxyethane (DME) was studied in detail.It was deduced that N-methyl-p-cyanoanilino radicals are formed and undergo three reactions: recombination into 1,2-bis(p-cyanophenyl)-1,2-dimethylhydrazine (2c, 21 percent), disproportionation (70 percent) into N-methyl-p-cyanoaniline (3c) and N-methylene-p-cyanoaniline (4c), and hydrogen atom abstraction (7 percent).A small amount of a p-semidine is thought to be formed also.These deductions were made from quantitative high-pressure LC measurements of yields of 2c, 3c, p-cyanoaniline (5c), and formaldehyde, the last two products arising from hydrolysis of 4c.Quantitative measurement of the conversion of 4c into 3c by hydrogenation and by trapping of radicals with butyl mercaptan was also used.Approximately 10 percent of 2e is formed in a solvent cage.Disproportionation also appears to occur within the cage.Less detailed studies were carried out with 1,4-diphenyl-1,4-dimethyl-2-tetrazene (1d) and 1,4-bis(p-bromophenyl)-1,4-dimethyl-2-tetrazene (1e).Decomposition of 1d led to 40 percent of N,N'-dimethyldiphenylhydrazine (2d, 10 percent in cage) and 40 percent of disproportionation products.The remaining 20 percent of the 1d is thought to form a p-semidine (N,N'-dimethyl-N-phenyl-1,4-benzenediamine) and the dibenzocarbazole related to it.Radicals from the decomposition of 1e led to 37 percent of 1,2-bis(p-bromophenyl)-1,2-dimethylhydrazine (2e, 10 percent in cage), 47 percent of disproportionation, and 16 percent of hydrogen abstraction.