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Caprolactone
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 ;
3D model (JSmol)	Interactive image;
ChEBI	CHEBI:17915 ;
ChEMBL	ChEMBL373123 ;
ChemSpider	9972 ;
ECHA InfoCard	100.007.217
KEGG	C01880 ;
PubChem CID	10401;
UNII	56RE988L1R ;
CompTox Dashboard (EPA)	DTXSID4027159 ;
	InChI InChI=1S/C6H10O2/c7-6-4-2-1-3-5-8-6/h1-5H2 Key: PAPBSGBWRJIAAV-UHFFFAOYSA-N ; 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). verify (what is ?) 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.^[3]

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.^[3] Another polymer is polyglecaprone, used as suture material in surgery.^[4]

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,^[5] and is also produced by the Khapra beetle as a pheromone.^[6] δ-caprolactone is found in heated milk fat.^[7]

An ether of caprolactone is used as a binder for AP/AN/Al rocket propellant HTCE: Hydroxy-Terminated Caprolactone Ether ^[8]

Safety

Caprolactone hydrolyses rapidly and the resulting hydroxycarboxylic acid displays unexceptional toxicity, as is common for the other hydroxycarboxylic acids.^[9] It is known to cause severe eye irritation. Exposure may result in corneal injury.^[1]

References

^ ^a ^b "ε-caprolactone SIDS Initial Assessment Report" (PDF). OECD. Archived from the original (PDF) on 2011-08-15. Retrieved 2017-10-12.
^ "Capa Monomer product data sheet" (PDF). Perstorp. 2015-02-27. Archived from the original (PDF) on 2017-02-02. Retrieved 2017-10-11.
^ ^a ^b Köpnick, Horst; Schmidt, Manfred; Brügging, Wilhelm; Rüter, Jörn; Kaminsky, Walter (2002). "Polyesters". Ullmann's Encyclopedia of Industrial Chemistry (6th ed.). Weinheim: Wiley-VCH. doi:10.1002/14356007.a21_227.
^ "glycolide E-caprolactone copolymer Summary Report". CureHunter. Retrieved 2017-10-11.
^ Mosandl, A.; Günther, C. (1989). "Stereoisomeric flavor compounds: structure and properties of gamma-lactone enantiomers". Journal of Agricultural and Food Chemistry. 37: 413–418. doi:10.1021/jf00086a031.
^ Nunez, M. Teresa; Martin, Victor S. (1990). "Efficient oxidation of phenyl groups to carboxylic acids with ruthenium tetraoxide. A simple synthesis of (R)-gamma-caprolactone, the pheromone of Trogoderma granarium". Journal of Organic Chemistry. 55 (6): 1928–1932. doi:10.1021/jo00293a044.
^ Parliament, Thomas H.; Nawar, Wassef W.; Fagerson, Irving S. (1965). "Delta-Caprolactone in Heated Milk Fat". Journal of Dairy Science. 48 (5): 615–616. doi:10.3168/jds.S0022-0302(65)88298-4.
^ HTCE
^ Miltenberger, Karlheinz (2002). "Hydroxycarboxylic Acids, Aliphatic". Ullmann's Encyclopedia of Industrial Chemistry (6th ed.). Weinheim: Wiley-VCH. doi:10.1002/14356007.a13_507.