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 $HCl$ at a temperature below $5 ° C$. Benzene diazonium chloride reacts with ${H}_{3}{PO}_{2}$ in aqueous medium to form benzene.