Which of the following is a Gattermann reaction?

1. $\mathrm{Ar} \mathrm{N}_{2}^{+} \mathrm{X}^{-} \stackrel{\mathrm{CuCl} / \mathrm{HCl}}{\longrightarrow} \mathrm{ArCl}+\mathrm{N}_{2} \uparrow$
2. $\mathrm{Ar} \mathrm{N}_{2}^{+} \mathrm{X}^{-} \stackrel{\mathrm{HBF}_{4}}{\longrightarrow} \mathrm{ArN}_{2}^{+} \mathrm{BF}_{4}^{-} \longrightarrow \mathrm{ArF}+\mathrm{N}_{2} \uparrow+\mathrm{BF}_{3}$
3. $\mathrm{Ar} \mathrm{N}_{2}^{+} \mathrm{X}^{-} \stackrel{\mathrm{Cu} / \mathrm{HBr}}{\longrightarrow} \mathrm{ArBr}+\mathrm{N}_{2} \uparrow$
4. $\mathrm{Ar} \mathrm{N}_{2}^{+} \mathrm{X}^{-} \frac{\mathrm{KI}}{\triangle} \longrightarrow \mathrm{ArI}+\mathrm{N}_{2} \uparrow+\mathrm{KX}$

Solution

In Gattermann reaction, chlorine or bromine can be introduced in the arene ring by treating the arene diazonium salt solution with corresponding halogen acid in the presence of copper powder.

Asked in: MHT CET 2020 (13 Oct Shift 1)

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