Concept:
Phenol reacts with chloroform and aqueous sodium hydroxide to give salicylaldehyde. This reaction is known as the Reimer-Tiemann reaction.
Step 1: Identify the reaction.
The reagents used are:
\[
\mathrm{Phenol + CHCl_3 + NaOH}
\]
These are characteristic reagents of the Reimer-Tiemann reaction.
Step 2: Formation of electrophile.
Under alkaline conditions, chloroform generates dichlorocarbene:
\[
:\mathrm{CCl_2}
\]
This electrophile attacks the activated phenoxide ion.
Step 3: Substitution occurs mainly at ortho position.
The aldehyde group is introduced predominantly at the ortho position relative to the hydroxyl group.
Step 4: Write the major product.
The final product formed is
\[
o\text{-Hydroxybenzaldehyde}
\]
commonly known as salicylaldehyde.
\[
{\text{Salicylaldehyde}}
\]
