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

Solution

Chemistry ma’am · 4 steps

Mild bromination of phenol goes mainly para, but Reimer–Tiemann puts the CHO group mainly ortho.

1. Reaction A. In a non-polar solvent like CS₂ at 273 K, Br₂ is only weakly polarised and phenol is not ionised. Only one Br goes on, at the ortho or para position. The para position is less crowded, so p-bromophenol is the major product.
2. Reaction B. With CHCl₃ and NaOH, dichlorocarbene (:CCl₂) forms and is attacked by the phenoxide ion. Attack happens mostly next to the O⁻ group, and hydrolysis turns the CHCl₂ group into CHO.
3. Product B. After acidification with H₃O⁺, the major product is salicylaldehyde (2-hydroxybenzaldehyde). This is the Reimer–Tiemann reaction.
4. So. A is p-bromophenol and B is salicylaldehyde, which is option (d).

The idea to keep. For phenol, check the conditions. Bromine in CS₂ or CHCl₃ in the cold gives monobromination, mainly para. Bromine water gives 2,4,6-tribromophenol. Reimer–Tiemann gives the ortho aldehyde.

Answer from the NTA final answer key. Solution by PrepWiser.