Nitrous Acid Deamination of 1,1-Disubstituted Aromatic Hydrazines

The nitrous acid deamination of N-methyl-N-phenylhydrazine, 1,1-diphenylhydrazine, and 9-aminocarbazole gave as products N-methylaniline, diphenylamine, and carbazole, respectively. N-tert-Butyl-N-phenylhydrazine gave N-tert-butylaniline and phenyl azide as products. These reactions were carried out in methanol, n-butanol, and benzene with isoamyl nitrite-HBF4 and isoamyl nitrite-acetic acid as the deamination reagents. Nitrous oxide was produced in all reactions. The yield of nitrous oxide is always less than that of the secondary amine formed in each reaction. This demonstrates that secondary amines are formed in two processes. It is proposed that the initially formed N-nitrosohydrazines can also give an N-diazonium ion. This species can decompose to give a nitrenium ion and nitrogen or phenyl azide and a carbonium ion. When the deamination of N-tertbutyl- N-phenylhydrazine was carried out in methanol, the carbonium ion fragment was trapped as the methyl ether. The formation of phenyl azide and methyl tert-butyl ether is evidence for the existence of an N-diazonium ion. The products expected from a singlet nitrenium ion derived from N-tert-butyl-N-phenylhydrazine were prepared. No evidence was found for their formation. Evidence is presented that nitrogen-centered radicals are not formed. The results indicate that the nitrenium ions generated by deamination are different from similar species produced from N-chloroanilines. This difference appears to be related to the manner in which the positive charge develops. It is proposed that the decomposition of the N-diazonium ion generates a nitrenium ion in which the positive charge is localized on nitrogen and that this leads to an enhanced rate of spin inversion. The secondary amines observed are formed by hydrogen atom abstraction by a triplet nitrenium ion and, as previously observed, with the formation of nitrous oxide.