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Skeletal formula of caprolactone
Ball-and-stick model of the caprolactone molecule
Preferred IUPAC name
Systematic IUPAC name
Other names
3D model (JSmol)
ECHA InfoCard 100.007.217
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)[2]
Miscible [1]
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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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 and is produced on a large scale as a precursor to caprolactam and polycaprolactone polymers.

Production and uses[edit]

The great majority of caprolactone is consumed, often in situ, as a precursor to caprolactam.[3] It is also a monomer used in the manufacture of highly specialised polymers. Ring-opening polymerization, for example, gives polycaprolactone.[4] Another polymer is polyglecaprone, used as suture material in surgery.[5]

Caprolactone is prepared industrially by Baeyer-Villiger oxidation of cyclohexanone with peracetic acid. The three main manufacturers are BASF in the United States, Daicel in Japan and the largest, Perstorp, in Sweden.


The dominant reaction for caprolactone is its conversion to caprolactam, billions of kilograms of which are produced annually.[citation needed] 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[edit]

Several other caprolactones are known, although none approaches the technological importance of ε-caprolactone. These isomers include 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,[6] and is also produced by the Khapra beetle as a pheromone.[7] δ-caprolactone is found in heated milk fat.[8]


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]


  1. ^ a b "ε-caprolactone SIDS Initial Assessment Report" (PDF). OECD. Archived from the original (PDF) on 2011-08-15. 
  2. ^ "Capa™ Monomer product data sheet" (PDF). Perstorp. 2015-02-27. Retrieved 2017-10-11. 
  3. ^ Template:Cite This is not correct!!encyclopedia
  4. ^ 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. 
  5. ^ "glycolide E-caprolactone copolymer Summary Report". CureHunter. Retrieved 2017-10-11. 
  6. ^ 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. 
  7. ^ 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. 
  8. ^ 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. 
  9. ^ Miltenberger, Karlheinz (2002). "Hydroxycarboxylic Acids, Aliphatic". Ullmann's Encyclopedia of Industrial Chemistry (6th ed.). Weinheim: Wiley-VCH. doi:10.1002/14356007.a13_507.