Trans-Cyclooctene

{{DISPLAYTITLE:trans-Cyclooctene}}

{{chembox

|Reference ={{cite web |url= http://www.sigmaaldrich.com/catalog/search/ProductDetail/ALDRICH/125482 |title= cis-Cyclooctene |publisher= Sigma-Aldrich }}

|Name =trans-Cyclooctene

|ImageFile =Trans-Cyclooctene.png

|ImageClass = skin-invert-image

|ImageSize = 344 px

|PIN =(E)-Cyclooctene

|OtherNames =trans-Cyclooctene

|Section1={{Chembox Identifiers

|ChemSpiderID = 10265272

|InChI=1S/C8H14/c1-2-4-6-8-7-5-3-1/h1-2H,3-8H2/b2-1+

|InChIKey = URYYVOIYTNXXBN-OWOJBTEDSA-N

|CASNo =931-89-5

|PubChem =5463599

|ChEBI = 73156

|EINECS = 213-245-5

|SMILES = C1CCC/C=C/CC1

}}

|Section2={{Chembox Properties

|C=8 | H=14

|Appearance = colorless liquid

|Density =0.848 g/mL

|MeltingPtC = -59

|BoilingPt = 143 °C (1 atm); 68-72 °C (100 torr)

}}

|Section3={{Chembox Hazards

|GHSPictograms = {{GHS02}}{{GHS08}}

|GHSSignalWord = Danger

}}

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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;{{cite journal |first1= Ulrich |last1= Neuenschwander |first2= Ive |last2= Hermans |doi= 10.1021/jo202176j |title= The conformations of cyclooctene: Consequences for epoxidation chemistry |journal=Journal of Organic Chemistry|volume= 76 |issue= 24 |pages= 10236–10240 |year= 2011 |pmid= 22077196 }} the ring-strain energies being 16.7 and 7.4 kcal/mol, respectively.{{cite journal | doi=10.1021/ma801693q | title=The Living ROMP of trans-Cyclooctene | year=2009 | last1=Walker | first1=Ron | last2=Conrad | first2=Rosemary M. | last3=Grubbs | first3=Robert H. | journal=Macromolecules | volume=42 | issue=3 | pages=599–605 | pmid=20379393 | pmc=2850575 | bibcode=2009MaMol..42..599W}}

style="margin-left:auto;margin-right:auto;" | 150px	align="right"|150px
align="center" | cis-Cyclooctene in chair conformation	(Rp)-trans-Cyclooctene in crown conformation

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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{{GoldBookRef |file= P04681 |title= Planar chirality}}) and the enantiomers can be separated.{{cite journal | doi=10.1021/ja00903a049 | title=Molecular Asymmetry of Olefins. I. Resolution of trans-Cyclooctene^1-3 | year=1963 | last1=Cope | first1=Arthur C. | last2=Ganellin | first2=C. R. | last3=Johnson | first3=H. W. | last4=Van Auken | first4=T. V. | last5=Winkler | first5=Hans J. S. | journal=Journal of the American Chemical Society | volume=85 | issue=20 | pages=3276–3279 }}{{cite journal | doi=10.1021/ja01078a044 | title=Molecular Asymmetry of Olefins. II. The Absolute Configuration of trans-Cyclooctene | year=1964 | last1=Cope | first1=Arthur C. | last2=Mehta | first2=Anil S. | journal=Journal of the American Chemical Society | volume=86 | issue=24 | pages=5626–5630 }}{{cite encyclopedia|title=(−)-Dichloro(ethylene)(α-methylbenzylamine)platinum(II)|author=Steven D. Paget |encyclopedia= Encyclopedia of Reagents for Organic Synthesis|year=2001|publisher= John Wiley & Sons|doi=10.1002/047084289X.rd119|isbn=0-471-93623-5 }} 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.