# Why cannot nitrosonium ion attack aniline in electrophylic aromatic substitution?

This is the nitrosonium ion, which is produced by the reaction of $\ce{NaNO2}$ and $\ce{HCl}$:

[Image source: Wikipedia]

And this is the reaction between aniline and nitrosonium:

[Image source: Wikipedia]

Cannot it take place as an EAS, and with substitution at the ortho or para positions? The amino group is a very good activating group for EAS after all.

Update: I forgot to mention that EAS is observed in case $\ce{-NR2}$ is attached to the ring in place of $\ce{-NH2}$.

• You certainly could. If I had to offer a post hoc justification, it's probably that at 0 degrees, the rate of ring substitution is extremely slow and cannot compete with N-attack. There is a similar selectivity question in, for example, the acylation of phenol. chemistry.stackexchange.com/questions/31531/… – orthocresol Jul 15 '16 at 9:26