8.6.1.2 N-Alkyl-N-nitrosoanilines (Fisher-Hepp Rearrangement)

The conjugate acid of the amine releases nitrosonium ion which reacts at para -position to give the p -nitroso product.

Mechanism

8.6.1.3 N-Arylazoanilines

N -Arylazoanilines undergo rearrangement in presence of an acid to produce 4-(2-aryldiazenyl)aniline. On treatment with acid, aryldiazonium ion is formed from the conjugate acid of amine, which migrates to the para position almost selectively.

8.6.1.4 N-Alkylanilines (Hofmann-Martius Rearrangement)

The mechanism of this rearrangement is same as described above, except the requirement of higher temperature (250-300°C).

Mechanism