Caprolactone
ε-Caprolactone or simply caprolactone is a lactone possessing a seven-membered ring. Its name is derived from caproic acid. This colorless liquid is miscible with most organic solvents and water. It was once produced on a large scale as a precursor to caprolactam.
Production and uses
Caprolactone is prepared industrially by Baeyer-Villiger oxidation of cyclohexanone with peracetic acid.Caprolactone is a monomer used in the production of highly specialised polymers. Ring-opening polymerization, for example, gives polycaprolactone. Another polymer is polyglecaprone, used as suture material in surgery.
Reactions
Although no longer economical, caprolactone was once produced as a precursor to caprolactam. Caprolactone is treated with ammonia at elevated temperatures to give the lactam:Carbonylation of caprolactone gives, after hydrolysis, pimelic acid. The lactone ring is easily opened with nucleophiles including alcohols and water to give polylactones and eventually the 6-hydroxyadipic acid.
Related compounds
Several other caprolactones are known, including α-, β-, γ-, and δ-caprolactones. All are chiral. -γ-caprolactone is a component of floral scents and of the aromas of some fruits and vegetables, and is also produced by the Khapra beetle as a pheromone. δ-caprolactone is found in heated milk fat.An ether of caprolactone is used as a binder for AP/AN/Al rocket propellant HTCE: Hydroxy-Terminated Caprolactone Ether