Question

Schemes $1$ and $2$ describe the conversion of P to Q a

nd R to S, respectively. Scheme $3$ describes the synthesis of T from Q and S. The total number of $\mathrm{Br}$ atoms in a molecule of T is_______

Answer 1

Scheme 1:

1. Product A is aniline, when it reacts with excess ${\mathrm{Br}}_2$ and water bromination occurs.
2. Because the ${\mathrm{NH}}_2$ group is an ortho and para directing group, the bromine group is bound to the ortho and para positions of the aniline. this results in the formation of$2,4,6$,tribromoaniline.
3. $2,4,6$,tribromoaniline produces $2,4,6$ tri Bromo benzene diazonium chloride (the diazonium salt) when it reacts with sodium nitrate $\left({\mathrm{NaNO}}_2\right)$ and hydrochloric acid ($\mathrm{HCl}$).
4. Aryl nitrile is created when benzene diazonium chloride interacts with cuprous cyanide ($\mathrm{CuCN}$)
5. $2,4,6$ tri Bromo benzene diazonium chloride reacts with $\mathrm{CuCN}$ to give $2,4,6$ tri Bromo benzonitrile.
6. Hydrolysis takes place as the next step in presence of ${{\mathrm{H}}_3}^{+}$ions. When benzonitrile is hydrolyzed, benzoic acid is formed.
7. When benzoic acid and ${\mathrm{SOCl}}_2$ react, benzoyl chloride is produced.

Scheme 2:

1. When benzene interacts with oleum, benzene sulfonic acid is produced.
2. To create sodium benzene sulfonate ion, we must now react benzene sulfonic acid with an aqueous solution of sodium hydroxide.
3. The resultant salt must be combined with solid sodium hydroxide before being heated to a high temperature. The result of this reaction is sodium phenoxide ion as the end product.
4. The sodium phenoxide ion is then converted to phenol by being acidified with aqueous acid.

Scheme-3:

1. S major i.e. $4-$bromophenol reacts with $\mathrm{NaOH}$ to give $2,4,6$ tribromo benzoyl chloride.
2. It further reacts to form $1-$Bromobenzyl, $2,4,6$ tribromo benzoate.
3. It has four bromine groups altogether.

Therefore, The total number of Br atoms in a molecule of T is $4$