Caprolactone

Caprolactone
Skeletal formula of caprolactone
Ball-and-stick model of the caprolactone molecule
Names
IUPAC name
2-oxepanone
Other names
epsilon-caprolactone
6-hexanolactone
hexano-6-lactone
1-oxa-2-oxocycloheptane
Identifiers
3D model (JSmol)
ChEBI
ChemSpider
ECHA InfoCard 100.007.217
KEGG
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)[1]
Miscible [2]
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

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.

Reactions

The major use of caprolactone is the production of polycaprolactones. These are split into two categories; the production of low molecular weight polycaprolactone polyols, used in specialty polyurethanes and coatings, and high molecular weight thermoplastics used in a variety of applications. There is published usage for caprolactone is its conversion to caprolactam, billions of kilograms of which are produced annually but not by this route.[6]

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.

Several other caprolactones are known, although none approaches the technological importance of ε-caprolactone. These isomers include alpha-, beta-, gamma-, delta-caprolactones. All are chiral. Gamma-caprolactone is component of flower aromas and an insect pheromone.[7] Delta-Caprolactone is found in heated milk fat.[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.

References

  1. ↑ https://www.perstorp.com/-/media/files/perstorp/pds/capa%20monomer/pds_capa%20monomer_eng-6142.pdf
  2. ↑ OECD SIDS [www.chem.unep.ch/irptc/sids/OECDSIDS/502443.pdf 502443 - epsilon-caprolactone]
  3. ↑ Josef Ritz, Hugo Fuchs, Heinz Kieczka, William C. Moran "Caprolactam" in Ullmann's Encyclopedia of Industrial Chemistry 2002, Wiley-VCH, Weinheim. doi:10.1002/14356007.a05_031
  4. ↑ Horst Köpnick, Manfred Schmidt, Wilhelm Brügging, Jörn Rüter, Walter Kaminsky "Polyesters" in Ullmann's Encyclopedia of Industrial Chemistry 2002, Wiley-VCH, Weinheim. doi:10.1002/14356007.a21_227
  5. ↑ http://www.curehunter.com/public/keywordSummaryC095495-glycolide-E-caprolactone-copolymer.do
  6. ↑ https://www.perstorp.com/en/products/plastic_materials/polyurethane_elastomers?Filterlevel0=Capa
  7. ↑ Leading reference: M. Teresa Nunez, Victor S. Martin (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, 1990, Volume 55, Issue 6, pp 1928–1932. doi:10.1021/jo00293a044
  8. ↑ Thomas H. Parliament, Wassef W. Nawar and Irving S. Fagerson (1965), Delta-Caprolactone in Heated Milk Fat Journal of Dairy Science Vol. 48 No. 5 pages 615-616.
  9. ↑ Karlheinz Miltenberger "Hydroxycarboxylic Acids, Aliphatic" in Ullmann's Encyclopedia of Industrial Chemistry, Wiley-VCH, Weinheim, 2005. doi:10.1002/14356007.a13_507
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