Caprolactone

Caprolactone

Skeletal formula of caprolactone Ball-and-stick model of the caprolactone molecule
Names
Preferred IUPAC name Oxepan-2-one
Other names Caprolactone ε-Caprolactone Hexano-6-lactone 6-Hexanolactone Hexan-6-olide 1-Oxa-2-oxocycloheptane
Identifiers
CAS Number	502-44-3 checkY
3D model (JSmol)	Interactive image
ChEBI	CHEBI:17915 checkY
ChEMBL	ChEMBL373123 checkY
ChemSpider	9972 checkY
ECHA InfoCard
E number
KEGG	C01880 checkY
PubChem CID	10401
UNII	56RE988L1R checkY
CompTox Dashboard (EPA)	{{#property:P3117}}
InChI InChI=1S/C6H10O2/c7-6-4-2-1-3-5-8-6/h1-5H2 checkY Key: PAPBSGBWRJIAAV-UHFFFAOYSA-N checkY InChI=1/C6H10O2/c7-6-4-2-1-3-5-8-6/h1-5H2 Key: PAPBSGBWRJIAAV-UHFFFAOYAG
SMILES C1CCC(=O)OCC1
Properties
Chemical formula	C6H10O2
Molar mass	114.14 g/mol
Density	1.030 g/cm3
Melting point	−1 °C (30 °F; 272 K)
Boiling point	241 °C (466 °F; 514 K)
Solubility in water	Miscible
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). ☒N verify (what is checkY☒N ?) Infobox references

ε-Caprolactone or simply caprolactone is a lactone (a cyclic ester) 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:

(CH₂)₅CO₂ + NH₃ → (CH₂)₅C(O)NH + H₂O

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. (R)-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

Safety

Caprolactone hydrolyses rapidly and the resulting hydroxycarboxylic acid displays unexceptional toxicity, as is common for the other hydroxycarboxylic acids. It is known to cause severe eye irritation. Exposure may result in corneal injury.