caprolactam

Caprolactam, also known as epsilon-caprolactam, is a lactam with the chemical formula C6H11NO and a seven-membered ring containing an amide group. It is a colorless to white crystalline solid that serves primarily as the monomer for producing nylon-6 by ring-opening polymerization, yielding polyamide 6, a widely used engineering plastic and fiber. Caprolactam is also employed as an intermediate in the synthesis of specialty polymers and resins.

Production and routes: The dominant industrial route to caprolactam involves the Beckmann rearrangement of cyclohexanone oxime, which is formed from cyclohexanone and hydroxylamine. Under acidic conditions, the oxime rearranges and cyclizes to give caprolactam, which is then purified for polymerization. An alternative, less common route involves the cyclization of 6-aminocaproic acid to caprolactam. These processes are integrated with large-scale production of nylon-6.

Properties: Caprolactam has a melting point near 70°C and is soluble in many organic solvents, with moderate solubility in water. Its amide functionality enables strong intermolecular hydrogen bonding, contributing to its physical properties and reactivity in polymerization.

Safety and handling: Caprolactam can be an irritant to skin, eyes, and the respiratory tract. Proper handling, adequate ventilation, and control of temperature and moisture are important in production and storage. It can polymerize exothermically under improper conditions, so inhibitors and controlled processing are used to maintain stability.

See also: Nylon-6, polyamide production.