Question

The major product (F) in the following reaction is

• A. o-Anisidine
• B. m-Anisidine
• C. p-Anisidine
• D. p-Chloro aniline

Hint:

Using a simple frame or just bolding for the box Key Points: Reaction of aryl halides lacking strong EWGs with NaNH$_2$/liq NH$_3$ proceeds via benzyne mechanism (Elimination-Addition). Benzyne formation involves deprotonation ortho to the leaving group, followed by elimination of the leaving group. Nucleophilic addition to the benzyne is regioselective, often guided by the inductive effects of substituents. Electron-withdrawing groups (like -OCH$_3$ via -I effect) direct the incoming nucleophile meta to themselves to best stabilize the intermediate carbanion. The product is m-anisidine.

Answer 1

The Correct Option is B

This reaction involves sodium amide (NaNH₂) in liquid ammonia, which are conditions for nucleophilic aromatic substitution proceeding via an elimination-addition (benzyne) mechanism.
(A) Elimination (Formation of Benzyne): The strong base, amide ion (NH₂^-), removes a proton from a carbon adjacent to the carbon bearing the leaving group (Cl). In m-chloroanisole, protons are available ortho to Cl (at C2 and C4 relative to OCH₃).Both pathways lead to benzyne intermediates where the triple bond involves C3. Example (deprotonation at C4): OCH₃- --> Benzyne 
(D) Addition (Attack by Nucleophile): The nucleophile (NH₂^-) attacks one of the carbons of the benzyne triple bond. The direction of addition is influenced by the substituent (-OCH₃).The methoxy group (-OCH₃) has a significant inductive electron-withdrawing effect (-I) which dominates in directing the addition to benzyne. This effect stabilizes the negative charge when it is further away from the electronegative oxygen. Therefore, the nucleophile (NH₂^-) preferentially adds to the carbon atom meta to the OCH₃ group (C3 in both benzyne possibilities), placing the resulting carbanion at C2 or C4. 
(G) Protonation: The resulting aryl anion is quickly protonated by the solvent (liquid NH₃) to give the final product. Addition of NH₂^- at the C3 position (meta to OCH₃) leads to the formation of m-anisidine (3-methoxyaniline).