Problem on Reactions of Haloarenes

Description:

Problem

Match the reactions of haloarenes given in column (A) to the type of reactions given in column (B).

(A)	(B)
(i)	(a) Nucleophilic Aromatic Substitution Reaction
(ii)	(b) Wurtz-Fittig Reaction
(iii)	(c) Sandmeyer Reaction
(iv)	(d) Electrophilic Aromatic Substitution Reaction

Solution

(i) → (d), (ii) → (a), (iii) → (b), (iv) → (c)

(i) It is an example of electrophilic aromatic substitution reaction. The electrophile generated is 𝐶𝑙+ which attacks the electron rich benzene ring giving substitution at ortho − and para − positions.

(ii) This reaction is an example of nucleophilic aromatic substitution reaction as the −Cl gets substituted by –OH group. Haloarenes are generally unreactive towards this reaction, except, in the presence of electron-withdrawing groups like −NO₂ when present at ortho and/or para positions. The negative charge on the carbon atom at ortho and para position is withdrawn by −NO₂ group and thus stabilizes it.

(iii) The formation of alkyl arene from the reaction of haloarene and haloalkane (in the presence of Na) is called Wurtz-Fitting reaction.

(iv) This reaction is Sandmeyer reaction where N₂⁺X⁻ of the diazonium salt gets substituted by −Cl when reacted with CuCl/HCl.