Question

Here, 2,4,6-tribromoaniline is a product of-
(A) electrophilic addition on ${{C}_{6}}{{H}_{5}}N{{H}_{2}}$
(B) electrophilic substitution on ${{C}_{6}}{{H}_{5}}N{{H}_{2}}$
(C) nucleophilic addition on ${{C}_{6}}{{H}_{5}}N{{H}_{2}}$
(D) nucleophilic substitution on ${{C}_{6}}{{H}_{5}}N{{H}_{2}}$

Answer 1

$N{{H}_{2}}$ group attached to the benzene ring is an electron donating group. As a result, electron density increases at ortho and para positions of aniline. 2,4,6-tribromoaniline is a result of bromination of aniline.

Complete answer:
${{C}_{6}}{{H}_{5}}N{{H}_{2}}$ is a chemical formula of anilines, also called as aminobenzene or phenylamine.
Electrophilic substitution reaction is an organic substitution reaction in which an electrophile substitutes another electrophile in an organic compound. Anilines(${{C}_{6}}{{H}_{5}}N{{H}_{2}}$)undergo the electrophilic substitution reactions such as halogenation, nitration and sulphonation. Bromination is an example of halogenation reaction.
The functional group (-$N{{H}_{2}}$) associated with aniline is an electron donating group and thus is very activating towards the electrophilic substitution reaction.
Due to various resonating structures of aniline, there is an excess of electron density at ortho- and para- positions of the benzene ring as compared to the meta- position. Hence, anilines are o- and p- directing towards electrophilic substitution reaction.

In this reaction shown above, when aniline comes close to bromine water, the bromine molecule develops a polarity within itself and $B{{r}^{+}}$ acts as an electrophile(electron loving specie) and attacks the electron rich ortho and para positions of ${{C}_{6}}{{H}_{5}}N{{H}_{2}}$. Bromine water gets decolourized and white precipitate 2,4,6-tribromoaniline is obtained at room temperature.

So, the correct answer is Option B.

Additional information:
In order to generate the mono-substituted product, a protection with acetyl chloride is required as shown below-

Note:
Nucleophilic substitution reaction is a chemical reaction where one nucleophile replaces another nucleophile.
Nucleophilic addition reaction is an additional reaction wherein a chemical species with an electrophilic double or triple bond reacts with a nucleophile.
An electrophilic addition reaction is an addition reaction in which a substrate is attacked by an electrophile.