Cyclooctene

Cyclooctene is a cycloalkene with an eight-membered ring. It can exist as either the cis- or trans-isomer with the cis-isomer normally being the predominant configuration. Cyclooctene is a smller cycloalkene in which the trans-isomer is stable at room temperature. Its most stable conformer is shaped like a crown ether with alternating equatorial and axial hydrogens very much like the chair conformation of cyclohexane.

trans-Cyclooctene was first synthesized on a preparatory scale by Arthur C. Cope from N,N,N-trimethylcyclooctylammonium iodide in a Hofmann elimination.

Other methods exist where the trans isomer is synthesized from the cis isomer in several synthetic steps. A photochemical method exists for this conversion in just one step:


 * [[Image:Trans-cyclooctene synthesis.svg|400px|Photochemical trans-cyclooctene synthesis Royzen 2008]]

Although the cis-trans equilibrium is unfavorable the reaction can be driven to completion by trapping the trans isomer by complexation with silver.