Which of the following compound will form a cyclic product on reaction with ethylene glycol?

Acetone

The correct answer is Option (1) → Acetone

Core Concept — Formation of Cyclic Acetals/Ketals

Ethylene glycol (a diol) reacts with aldehydes or ketones in the presence of acid to form cyclic acetals (from aldehydes) or cyclic ketals (from ketones).

This reaction is used as a carbonyl protection method.

Only compounds having a carbonyl group (C=O) undergo this reaction.

Option 1: Acetone

Acetone is a ketone and contains a carbonyl group. It reacts with ethylene glycol under acidic conditions to form a five-membered cyclic ketal. This is the correct compound.

Option 2: Ethyl ether

Ethers do not have a carbonyl group. They are generally inert toward ethylene glycol under these conditions. So no cyclic product forms.

Option 3: Benzoic acid

Carboxylic acids do not form cyclic acetals/ketals with diols. They may form esters, but not the characteristic cyclic acetal structure. Hence, not correct.

Option 4: Benzyl alcohol

Alcohols lack a carbonyl group required for acetal formation. They cannot react with ethylene glycol to give a cyclic acetal. So this is incorrect.