When phenol is treated with chloroform in the presence of \(NaOH\), the major product formed is?

Salicylaldehyde

The correct answer is option 3. Salicylaldehyde.

When phenol is treated with chloroform (\(CHCl_3\)) in the presence of \(NaOH\), it undergoes a Reimer-Tiemann reaction. In this reaction, phenol reacts with chloroform in the presence of a strong base like sodium hydroxide to form salicylaldehyde as the major product. The Reimer-Tiemann reaction can be represented as:

Mechanism:

It involves electrophilic substitution of the aromatic nucleus, the electrophile being dichloro carbene \((:CCl_2)\) (carbon has only sextet of electrons), formed by the action of strong alkali on chloroform.