Cyclooctane

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Cyclooctane
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Density 0.840 g/cm3[1]
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Template:Longitem −91.4·10−6 cm3/mol
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Cyclooctane is a cycloalkane with the molecular formula (CH2)8.[2] It is a simple colourless hydrocarbon, but it is often a reference compound for saturated eight-membered ring compounds in general.

Cyclooctane has a camphoraceous odor.[3]

Conformations

Script error: No such module "labelled list hatnote". The conformation of cyclooctane has been studied extensively using computational methods. Hendrickson noted that "cyclooctane is unquestionably the conformationally most complex cycloalkane owing to the existence of many conformers of comparable energy". The boat-chair conformation (below) is the most stable form.[4] Allinger and co-workers confirmed this.[5] The crown conformation (below)[6] is slightly less stable. Among the many compounds exhibiting the crown conformation (structure II) is S8, elemental sulfur.

File:Cyclooctane boat-chair conformation.svg File:Cyclooctane-boat-chair-3D-balls.png File:Cyclooctane crown conformation.svg File:Cyclooctane-crown-3D-balls.png
Boat-chair[7] Crown[7]
File:Cyclooctane tub conformation.svg File:Cyclooctane boat-boat conformation.svg File:Cyclooctane twist boat-chair conformation.svg File:Cyclooctane twist chair-chair conformation.svg
Tub[8] Boat-boat[7] Twist boat-chair[7] Twist chair-chair[7]

Synthesis and reactions

The main route to cyclooctane derivatives involves the dimerization of butadiene, catalysed by nickel(0) complexes such as nickel bis(cyclooctadiene).[9] This process affords, among other products, 1,5-cyclooctadiene (COD), which can be hydrogenated. COD is widely used for the preparation of precatalysts for homogeneous catalysis. The activation of these catalysts under H2, produces cyclooctane, which is usually discarded or burnt:

C8H12 + 2 H2 → C8H16

Cyclooctane participates in no reactions except those typical of other saturated hydrocarbons, combustion and free radical halogenation. Work in 2009 on alkane functionalisation, using peroxides such as dicumyl peroxide, has opened up the chemistry to some extent, allowing for example the introduction of a phenylamino group.[10]

File:CyclooctaneAmination.png
Amination of cyclooctane by nitrobenzene

References

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  1. ECHA REACH
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  6. IUPAC, Compendium of Chemical Terminology, 5th ed. (the "Gold Book") (2025). Online version: (2006–) "crown conformation". Script error: No such module "CS1 identifiers".Script error: No such module "TemplatePar".
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  9. Thomas Schiffer, Georg Oenbrink, “Cyclododecatriene, Cyclooctadiene, and 4-Vinylcyclohexene” in Ullmann’s Encyclopedia of Industrial Chemistry, 2005, Wiley-VCH, Weinheim. Script error: No such module "CS1 identifiers"..
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