Question

What happens in the following reaction?

• A. No reaction happens as tertiary amines do not react with $HONO$
• B. There is a nucleophilic aromatic substitution
• C. The product is based on Hofmann elimination
• D. There is an electrophilic aromatic substitution

Answer 1

The correct option is D

There is an electrophilic aromatic substitution

The substrate is a tertiary amine and in general, tertiary amines do not react with nitrous acid. This case is slightly different though.
The mixture of $NaN{O}_{2}andHCl$ gives $HONO$, which on protonation, yields the nitrosyl cation:

The nitrogen attached to the benzene – in this case – is highly activating owing to the presence of the lone pair of electrons, which conjugate into the ring. So, an electrophilic aromatic substitution reaction happens such that the major product (95% yield) is N,N-dimethyl-4-nitrosoaniline.