Caprolactam when heated at high temperature in presence of water, gives

We need to identify the product formed when caprolactam is heated at high temperature in the presence of water.

Caprolactam is a cyclic amide (lactam) with 6 carbon atoms. When heated with water at high temperature, it undergoes ring-opening polymerization:

The water initiates the hydrolysis of the amide bond in caprolactam, opening the ring. The opened ring monomers then undergo condensation polymerization to form a long-chain polyamide.

$$n \text{ Caprolactam} \xrightarrow{\Delta, \text{H}_2\text{O}} \text{Nylon 6}$$

The product is Nylon 6 (polycaprolactam), which is a polyamide with the repeating unit $$-[\text{NH}(\text{CH}_2)_5\text{CO}]_n-$$.

Note: Nylon 6,6 is made from hexamethylenediamine and adipic acid, not from caprolactam.

The correct answer is Option 4: Nylon 6.