Explain the chemical reactions of benzene-diazonium chloride.

(N/A) The chemical reactions of diazonium salts are broadly classified into two categories: $(A)$ reactions involving the displacement of nitrogen and $(B)$ reactions involving the retention of the diazo group.
$(a)$ Reactions involving displacement of nitrogen:
The diazonium group is an excellent leaving group and is substituted by other groups such as $Cl^-$,$Br^-$,$I^-$,$CN^-$,and $OH^-$. The nitrogen gas $(N_2)$ is evolved during these reactions.
$(i)$ Sandmeyer reaction:
Nucleophiles like $Cl^-$,$Br^-$,and $CN^-$ can be introduced into the benzene ring by treating the diazonium salt solution with the corresponding cuprous halide ($Cu_2Cl_2$,$Cu_2Br_2$) or cyanide $(CuCN)$ in the presence of the respective acid ($HCl$,$HBr$) or $KCN$.
$(ii)$ Gatterman reaction:
Chlorine or bromine can be introduced into the benzene ring by treating the diazonium salt solution with the corresponding halogen acid in the presence of copper powder. This is known as the Gatterman reaction.