Surf Wiki
Save to docs
general/cycloalkenes

From Surf Wiki (app.surf) — the open knowledge base

Trans-Cyclooctene

trans-Cyclooctene is a cyclic hydrocarbon with the formula [–(CH2)6CH=CH–], where the two C–C single bonds adjacent to the double bond are on opposite sides of the latter's plane. It is a colorless liquid with a disagreeable odor.

Cyclooctene is notable as the smallest cycloalkene that is readily isolated as its trans-isomer. The cis-isomer is much more stable; the ring-strain energies being 16.7 and 7.4 kcal/mol, respectively.

*cis*-Cyclooctene
in *chair* conformation(*Rp*)-*trans*-Cyclooctene
in *crown* conformation

A planar arrangement of the ring carbons would be too strained, and therefore the stable conformations of the trans form have a bent (non-planar) ring. Computations indicate that the most stable "crown" conformation has the carbon atoms alternately above and below the plane of the ring. A "half-chair" conformation, with about 6 kcal/mol higher energy, has carbons 2,3,5,6, and 8 on the same side of the plane of carbons 1,4, and 7.

All conformations of trans-cyclooctene are chiral (specifically, what some call planar-chiral) and the enantiomers can be separated. In theory, conversion of between the enantiomers can be done, without breaking any bonds, by twisting the whole –CH=CH– group, rigidly, by 180 degrees. However, that entails passing one of its hydrogens through the crowded ring.

Preparation

trans-Cyclooctene was first synthesized on a preparatory scale by Arthur C. Cope with a Hofmann elimination reaction of N,N,N-trimethylcyclooctylammonium iodide. The reaction gives a mixture of cis and trans isomers, and the trans isomer is selectively trapped as a complex with silver nitrate.

Other methods exist where the trans isomer is synthesized from the cis isomer in several synthetic steps. For instance, it can be prepared in almost 100% yield by converting the cis isomer to 1,2-epoxycyclooctane ("cyclooctene oxide") followed by reactions with lithium diphenylphosphide () and with methyl iodide . (Similar procedures can give ** isomers of 1,4-cyclooctadiene and 1,5-cyclooctadiene).

In addition, a photochemical method exists for the direct cis–trans isomerisation. Although this equilibrium strongly favours the more stable cis form, the reaction can be driven towards the trans form by trapping with silver ions.

Reactions

Because of the higher internal strain on the double bond, the trans isomer is more reactive than the cis isomer and of typical unsaturated hydrocarbons. For instance, its double bond will rapidly add tetrazine and its derivatives. The compound also readily polymerizes with a ruthenium-based initiator.

References

References

  1. "''cis''-Cyclooctene". [[Sigma-Aldrich]].
  2. (2011). "The conformations of cyclooctene: Consequences for epoxidation chemistry". [[Journal of Organic Chemistry]].
  3. (2009). "The Living ROMP of ''trans''-Cyclooctene". [[Macromolecules (journal).
  4. "Planar chirality".
  5. (1963). "Molecular Asymmetry of Olefins. I. Resolution of ''trans''-Cyclooctene1-3". [[Journal of the American Chemical Society]].
  6. (1964). "Molecular Asymmetry of Olefins. II. The Absolute Configuration of ''trans''-Cyclooctene". [[Journal of the American Chemical Society]].
  7. Steven D. Paget. (2001). "(−)-Dichloro(ethylene)(α-methylbenzylamine)platinum(II)". John Wiley & Sons.
  8. (1969). "''trans''-Cyclooctene".
  9. (1973). "Phosphorus betaines derived from cycloheptene and cyclooctene oxides. Inversion of cyclooctene". [[Journal of Organic Chemistry]].
  10. (1969). "Photoisomerization of ''cis''-cyclooctene to ''trans''-cyclooctene". [[Journal of Organic Chemistry]].
  11. (2008). "A photochemical synthesis of functionalized ''trans''-cyclooctenes driven by metal complexation". [[Journal of the American Chemical Society]].
  12. (2013). "''trans''-Cyclooctene — A stable, voracious dienophile for bioorthogonal labeling". [[Current Opinion in Chemical Biology]].
Info: Wikipedia Source

This article was imported from Wikipedia and is available under the Creative Commons Attribution-ShareAlike 4.0 License. Content has been adapted to SurfDoc format. Original contributors can be found on the article history page.

cycloalkenes foul-smelling-chemicals
Want to explore this topic further?

Ask Mako anything about Trans-Cyclooctene — get instant answers, deeper analysis, and related topics.

Research with Mako

Free with your Surf account

Content sourced from Wikipedia, available under CC BY-SA 4.0.

This content may have been generated or modified by AI. CloudSurf Software LLC is not responsible for the accuracy, completeness, or reliability of AI-generated content. Always verify important information from primary sources.

Report