Question

How will you convert phenol to salicylaldehyde?

Hint:

The Reimer–Tiemann reaction introduces a \(-\text{CHO}\) group at the ortho position of phenols using CHCl\(_3\) and NaOH.

Answer 1

Step 1: Phenol is treated with chloroform (CHCl\(_3\)) and aqueous sodium hydroxide (NaOH) and heated.
Step 2: Under alkaline conditions, chloroform generates dichlorocarbene (\(:\text{CCl}_2\)), which acts as an electrophile.
Step 3: The electrophile attacks the ortho position of phenol (–OH group is ortho/para directing).
Step 4: On subsequent hydrolysis, the ortho-substituted product forms salicylaldehyde (o-hydroxybenzaldehyde). \[ \text{Phenol} \xrightarrow[\text{NaOH}]{\text{CHCl}_3,\ \Delta} \text{Salicylaldehyde} \]