Question

When the following compound reacts with 1 mole of $HCl$:

• A. Protonation takes place at Nitrogen 1
• B. Protonation takes place at nitrogen 2
• C. Protonation cannot take place
• D. Protonation takes place at both the nitrogens

Answer 1

The correct option is B Protonation takes place at nitrogen 2

Since one mole of $HCl$ i.e., one $H^{+}$ is there, so protonation will take place at only one nitrogen.
The lone pair on nitrogen 1 is involved in conjugation whereas it is not the case for nitrogen 2.

More the delocalisation, less is the availability of lone pair for donation, and less likely is the protonation to take place.
So, Nitrogen 2 is more basic and protonation takes place at that position.