Question

The major product formed in the following reaction is 

• A. (A)
• B. (B)
• C. (C)
• D. (D)

Hint:

In nucleophilic substitution reactions, especially with sodium amide (\( \text{NaNH}_2 \)) in liquid ammonia, halogens are replaced by nucleophilic groups like amines.

Answer 1

The Correct Option is C

Reaction conditions: NaNH₂ in liquid NH₃

NaNH₂ is a strong base that can:

1. Deprotonate acidic hydrogens
2. Facilitate nucleophilic aromatic substitution
3. Promote intramolecular cyclization

Analyzing the substrate:

• Ortho-chlorobenzene with a -(CH₂)₃CN side chain
• The CN group at the end of the chain
• Chlorine is ortho to the side chain

Mechanism possibilities:

Option 1: Nucleophilic aromatic substitution (SNAr)

• NaNH₂ can replace Cl with NH₂
• Would give option (A) or (B)
• However, simple SNAr would give (A)

Option 2: Intramolecular cyclization

• The CN group can be deprotonated (α to CN is acidic)
• NaNH₂ deprotonates the CH₂ α to CN
• The resulting carbanion can attack the aromatic ring ortho to Cl
• This leads to nucleophilic aromatic substitution with ring closure
• Forms an indane (5-membered ring fused to benzene)

Mechanism for cyclization:

1. NaNH₂ deprotonates CH₂ adjacent to CN (most acidic position)
2. Carbanion attacks ipso carbon (where Cl is attached)
3. Cl leaves as the ring closes
4. Forms 1-cyanoindane structure

Product analysis:

(A): Simple SNAr replacing Cl with NH₂ - less favorable than cyclization

(B): Para-substituted product - wrong regiochemistry

(C): 1-Cyanoindane - indane ring with CN at position 1

• Formed by intramolecular cyclization
• Most favored product 

(D): Tetralone - would require CN hydrolysis and different reaction path

Answer: (C)