What happens when phenol reacts with potassium persulphate? 

Quinol is produced 

The correct answer is option 4. Quinol is produced.

When phenol reacts with potassium persulfate \((K_2S_2O_8)\) under appropriate conditions, the major product formed is Hydroquinone (also known as quinol)

Here is a breakdown of the reaction:

Reaction Type: This reaction is known as the Elbs persulfate oxidation. It's an oxidative coupling reaction that occurs in an alkaline medium.

Role of Potassium Persulfate: \(K_2S_2O_8\) acts as an oxidizing agent, but it doesn't directly oxidize the phenol molecule. Instead, it generates sulfate radicals \((SO_4^-)\) in the presence of a base \((OH^-)\).

Oxidation by Sulfate Radicals: The sulfate radicals are the actual oxidizing species that attack the phenol molecule.

Formation of Hydroquinone: The reaction involves the removal of two hydrogen atoms, one from each aromatic ring, at the para positions relative to the hydroxyl group in the starting phenol molecule. This coupling of two phenol rings and the loss of hydrogens result in the formation of hydroquinone.