cis-Cyclooctene is a cycloalkene with the formula (CH2)6(CH)2. It is a colorless liquid that is used industrially to produce a polymer. It is also a ligand in organometallic chemistry.

IUPAC name
Other names
3D model (JSmol)
ECHA InfoCard 100.012.040
EC Number
  • 213-243-4
Molar mass 110.200 g·mol−1
Density 0.846 g/mL
Melting point −16 °C (3 °F; 257 K)
Boiling point 145 to 146 °C (293 to 295 °F; 418 to 419 K)
GHS pictograms
GHS Signal word Danger
H226, H304
P210, P233, P240, P241, P242, P243, P280, P301+310, P303+361+353, P331, P370+378, P403+235, P405, P501
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Infobox references

Cyclooctene is the smallest cycloalkene that can be isolated as both the cis- and trans-isomer.[2] Trans-Cyclooctene is shaped like the 8-carbon equivalent chair conformation of cyclohexane.

cis-Cyclooctene          trans-Cyclooctene   

Uses and reactions

Cyclooctene undergoes ring-opening metathesis polymerization to give polyoctenamers, which are marketed under the name Vestenamer.[3]

cis-Cyclooctene (COE) is a substrate known for quite selectively forming the epoxide, as compared to other cycloalkenes, e.g. cyclohexene. Low amounts of radical by-products are found only. This behaviour is attributed to the difficulty of functionalizing allylic CH centers, which almost orthogonal allylic C-H bonds. Therefore, if radicals are around, they tend to form epoxide via an addition-elimination mechanism.[2]

It is used as an easily displaced ligand in organometallic chemistry, e.g. chlorobis(cyclooctene)rhodium dimer and chlorobis(cyclooctene)iridium dimer.


  1. "cis-Cyclooctene". Sigma-Aldrich.
  2. Neuenschwander, Ulrich; Hermans, Ive (2011). "The Conformations of Cyclooctene: Consequences for Epoxidation Chemistry". J. Org. Chem. 76 (24): 10236–10240. doi:10.1021/jo202176j.
  3. Lionel Delaude, Alfred F. Noels (2005). "Metathesis". Kirk-Othmer Encyclopedia of Chemical Technology. Weinheim: Wiley-VCH. doi:10.1002/0471238961.metanoel.a01.CS1 maint: uses authors parameter (link)
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