Question

The major product P formed in the following reaction is

• A. A
• B. B
• C. C
• D. D
• E. E

Hint:

In biphenyl: - Phenyl group is ortho/para directing - Para position is preferred due to less steric hindrance - Multiple substitutions follow directing effects cumulatively

Answer 1

The Correct Option is B

Concept: This is an example of electrophilic aromatic substitution (EAS) on biphenyl. Key points:
• Biphenyl consists of two benzene rings connected by a single bond
• The ortho and para positions relative to the phenyl group are activated
• Steric hindrance disfavors ortho substitution
• Hence, substitution occurs mainly at the para position

Step 1: First chlorination \[ \text{Cl}_2/\text{FeCl}_3 \Rightarrow \text{electrophile } Cl^+ \] The phenyl group activates the ring and directs substitution at:
• Ortho (hindered)
• Para (favored) Thus, first substitution occurs at para position.

Step 2: Second chlorination Now the ring already contains:
• One phenyl group (activating)
• One chlorine (deactivating but ortho/para directing) Combined directing effect leads to substitution at:
• Para position on the second ring Final Product:
• Chlorine substituted at para positions of both rings Hence, option (B) is correct.