Question

Identify the major products A and B respectively in the following reactions of phenol:

(B) \( \frac{\text { (i) } CHCl _{3}, NaOH }{\text { (ii) } H _{3} O ^{+}} \) \( \frac{ Br _{2} \text { in } CS _{2}}{273 K } \rightarrow \) (A)

• A.
• B.
• C.
• D.

Answer 1

The correct option is B

Product A:
Phenol undergoes bromination in $C{S}_2$ to give para-bromophenol. Though $OH$ is a ortho/para directing group, para product is major due to the less steric hindrance.

Product B:
It is a Reimer-Tiemann reaction. In this reaction, phenol gets converted to salicylaldehyde in the presence of $CHC{l}_3+Aq.NaOH$ followed by hydrolysis.
It is an electrophilic substitution reaction, reaction intermediate dichloro carbene is formed and acts as an electrophile.

In the Reimer-Tiemann reaction, the phenoxide ion formed will show mesomeric and inductive effect hence, the reaction might take place at ortho or para position. But as we know, +I-effect decreases with increasing distance, therefore the ortho position will be electron rich and the incoming electrophile will attack at the ortho position. Therefore, formylation will take place at the ortho position.


So option (b) is the correct answer