Compound A from the following reaction sequence is :

When aniline treated with bromine, the reaction results in the formation of $2,4,6$-tribromo phenylamine. This reaction is an example of bromination. The process of conversion of a primary aromatic amino compound into a diazonium salt is known as diazotization. This process is carried out by adding an aqueous solution of sodium nitrite to a solution of primary aromatic amine (e.g., aniline) in excess of $\mathrm{HCl}$ at a temperature below $5°\mathrm{C}$. Benzene diazonium chloride reacts with ${\mathrm{H}}_3{\mathrm{PO}}_2$ in aqueous medium to form benzene.