Chemistry:Caprolactone

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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
3D model (JSmol)
ChEBI
ChEMBL
ChemSpider
KEGG
UNII
Properties
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)[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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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

  1. 1.0 1.1 "ε-caprolactone SIDS Initial Assessment Report". OECD. http://www.chem.unep.ch/irptc/sids/OECDSIDS/502443.pdf. 
  2. "Capa Monomer product data sheet". Perstorp. 2015-02-27. https://www.perstorp.com/-/media/files/perstorp/pds/capa%20monomer/pds_capa%20monomer_eng-6142.pdf. 
  3. 3.0 3.1 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. 
  4. "glycolide E-caprolactone copolymer Summary Report". CureHunter. http://www.curehunter.com/public/keywordSummaryC095495-glycolide-E-caprolactone-copolymer.do. 
  5. 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. 
  6. 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. 
  7. 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. 
  8. HTCE
  9. Miltenberger, Karlheinz (2002). "Hydroxycarboxylic Acids, Aliphatic". Ullmann's Encyclopedia of Industrial Chemistry (6th ed.). Weinheim: Wiley-VCH. doi:10.1002/14356007.a13_507.