JEE Main · 2023 · 30 Jan 2023 · Shift 1 · Polymers

Caprolactam is the cyclic amide (lactam) of 6-aminohexanoic acid, a seven-membered ring carrying one amide linkage. On heating with a trace of water at high temperature, the water opens the ring to the amino acid, whose amino and carboxyl ends then condense over and over in a ring-opening polymerisation. Each monomer contributes one $-\mathrm{NH}-(\mathrm{C}{\mathrm{H}}_2{)}_5-\mathrm{CO}-$ unit, so a single six-carbon repeating unit builds the chain. Teflon is the fluorocarbon polymer of tetrafluoroethene, Dacron is a polyester of ethylene glycol with terephthalic acid, and nylon-6,6 needs two different six-carbon monomers (hexamethylenediamine and adipic acid). The polymer formed from the single monomer caprolactam is nylon-6.