Cyclooctatetraene
General
Systematic name	1,3,5,7-cyclooctatetraene
Other names	COT, [8]-annulene
Molecular formula	C8H8
SMILES	C1=C/C=CC=C/C=C1
Molar mass	104.15 g/mol
Appearance	Clear yellow
CAS number	[629-20-9]
Properties
Density and phase	0.9250 g/cm³, liquid
Solubility in water	immiscible
Melting point	-27 °C (246 K)
Boiling point	142 - 143 °C (415 - 416 K)
Hazards
MSDS	External MSDS
EU classification	Flammable (F) Carc. Cat. 1 Muta. Cat. 2 Toxic (T)
NFPA 704
R-phrases	R45, R46, R11, R36/38, R48/23/24/25, R65
S-phrases	S53, S45
Flash point	−11 °C
Autoignition temperature	561 °C
RTECS number	CY1400000
Related compounds
Related hydrocarbons	cyclooctane
Except where noted otherwise, data are given for materials in their standard state (at 25°C, 100 kPa) Infobox disclaimer and references

1,3,5,7-Cyclooctatetrene (COT) is an unsaturated derivative of cyclooctane, with the formula C₈H₈. It is also known as [8]annulene. This polyunsaturated hydrocarbon is a colorless to light yellow flammable liquid at room temperature. Because of its stoichiometric relationship to benzene, COT has been the subject of much research and some controversy. IUPAC nomenclature is a system of naming chemical compounds and of describing the science of chemistry in general. ... A chemical formula (also called molecular formula) is a concise way of expressing information about the atoms that constitute a particular chemical compound. ... The simplified molecular input line entry specification or SMILES is a specification for unambiguously describing the structure of chemical molecules using short ASCII strings. ... Molar mass is the mass of one mole of a chemical element or chemical compound. ... 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The autoignition temperature, or the ignition temperature of a substance is the lowest temperature at which a chemical will spontaneously ignite in a normal atmosphere, without an external source of ignition, such as a flame or spark. ... RTECS, also known as Registry of Toxic Effects of Chemical Substances, is a database of toxicity information compiled from the open scientific literature that is available for charge. ... Hydrocarbons are refined at oil refineries and processed at chemical plants A hydrocarbon is a chemical compound that consists only of the elements carbon (C) and hydrogen (H). ... In chemistry, the standard state of a material is its state at 1 bar (100 kilopascals) and 25 degrees Celsius (298. ... In chemistry, saturation has four different meanings: In physical chemistry, saturation is the point at which a solution of a substance can dissolve no more of that substance and additional amounts of that substance will appear as a precipitate. ... This article assumes an understanding of algebra, analytic geometry, and the limit. ... Annulenes are completely conjugated monocyclic hydrocarbons. ... Hydrocarbons are refined at oil refineries and processed at chemical plants A hydrocarbon is a chemical compound that consists only of the elements carbon (C) and hydrogen (H). ... Benzene, also known as benzol, is an organic chemical compound with the formula C6H6. ...

Unlike benzene, C₆H₆, however, cyclooctatetraene, C₈H₈, is not aromatic. Its reactivity is characteristic of an ordinary polyene, i.e. it undergoes addition reactions. Benzene, by contrast, characteristically undergoes substitution reactions, not additions. Aromaticity is a chemical property in which a conjugated ring of unsaturated bonds, lone pairs, or empty orbitals exhibit a stabilization stronger than would be expected by the stabilization of conjugation alone. ... Polyenes are poly-unsaturated organic compounds that contain one or more sequences of alternating double and single carbon-carbon bonds. ... An addition reaction, in chemistry, is in its simplest terms an organic reaction where two or more molecules combine to form a larger one. ... In a substitution reaction, a group of a particular compound is replaced by another group. ...

History

1,3,5,7-cyclooctatetrene was initially synthesized by Richard Willstätter at Munich in 1905. ^[1] Willstätter noted that the compound did not exhibit the expected aromaticity. Between 1939 and 1943, chemists throughout the US unsuccessfully attempted to synthesize COT. They rationalized their lack of success with the conclusion that Willstätter had not actually synthesized the compound but instead its isomer, styrene. Willstätter responded to these reviews in his autobiography, where he noted that the American chemists were 'untroubled' by the reduction of his cyclooctatetraene to cyclooctane (a reaction impossible for styrene). In 1947, Walter Reppe at Ludwigshafen at last repeated Willstätter's synthesis. Richard Willstätter Richard Martin Willstätter (August 13, 1872 – August 3, 1942) was a German chemist whose study of the structure of chlorophyll and other plant pigments won him the 1915 Nobel Prize for Chemistry. ... C8H8 redirects here. ...

Structure and Bonding

Cyclooctatetraene in its native "tub-shaped" conformation.

Early studies demonstrated that COT did not display the chemistry of an aromatic compound ^[2], yet early electron diffraction experiments concluded that the C-C bond distances were identical ^[3]. However, X-Ray diffraction data from H.S. Kaufman demonstrated cyclooctatetraene to contain two distinct C-C bond distances ^[4]. This result indicated that COT is an annulene with fixed alternating single and double C-C bonds. In its normal state, cyclooctatetraene is non-planar and adopts a tub-shaped confirmation. Annulenes are completely conjugated monocyclic hydrocarbons. ...

Chemistry

Richard Willstätter's original synthesis

Richard Willstätter's original synthesis (4 consecutive elimination reactions on a cycloctane framework) gives relatively low yields. Reppe's synthesis of cyclooctatetraene involved treating acetylene at high pressure with a warm mixture of nickel cyanide and calcium carbide was much better, with chemical yields near 90% ^[5]. An elimination reaction is a type of organic reaction in which two substituents are removed from a molecule in either a one or two-step mechanism. ... Acetylene (systematic name: ethyne) is the simplest alkyne hydrocarbon, consisting of two hydrogen atoms and two carbon atoms connected by a triple bond. ... Calcium carbide is a chemical compound with the chemical formula CaC2. ... Yield in chemistry, also known as chemical yield and reaction yield, is the amount of product obtained in a chemical reaction. ...

Because COT is unstable and easily forms explosive organic peroxides, a small amount of hydroquinone is usually added to commercially available material. Testing for peroxides is advised when using a previously opened bottle; white crystals around the neck of the bottle may be composed of the peroxide, which may explode when mechanically disturbed. The general structure of an organic peroxide. ... Hydroquinone, also benzene-1,4-diol, is an aromatic organic compound which is a type of phenol, having the chemical formula C6H4(OH)2. ...

COT reacts with peroxy acids, yielding epoxides. It easily undergoes addition reactions. Furthermore, a stable polyacetylene has been synthesized via the ring-opening polymerization of an alkyl-substituted cyclooctatetraene ^[6]. A peroxy acid, is an acid in which an acidic -OH group has been replaced by an -OOH group. ... An epoxide is a cyclic ether with only three ring atoms. ... Polyacetylene (PA) is conducting polymer of the rigid-rod polymer host family. ... In chemistry, ring-opening polymerization is a subset of addition polymerization, in that an end of a growing polymer chain acts as a reactive center that can react with additional monomers to propagate the chain. ...

Reppe's Reaction

Cyclooctatetraenide anion

COT readily reacts with potassium metal to form the salt K₂COT, which contains the dianion C₈H₈^2-. The dianion is both planar in shape and aromatic with a Huckel electron count of 10. Cyclooctatetraene forms complexes with some metals, including yttrium and lanthanides. One-dimensional Eu-COT sandwiches have been described as nanowires ^[7]. The sandwich compounds U(COT)₂, or uranocene and Fe(COT)₂, are known. General Name, Symbol, Number potassium, K, 19 Chemical series alkali metals Group, Period, Block 1, 4, s Appearance silvery white Atomic mass 39. ... In chemistry, an aromatic molecule is one in which electrons are free to cycle around circular arrangements of atoms, which are alternately singly and doubly bonded to one another. ... Synthesis of copper(II)-tetraphenylporphine, a metal complex, from tetraphenylporphine and copper(II) acetate monohydrate. ... General Name, Symbol, Number yttrium, Y, 39 Chemical series transition metals Group, Period, Block 3, 5, d Appearance silvery white Atomic mass 88. ... The lanthanide series comprises the 15 elements from lanthanum to lutetium on the periodic table, with atomic numbers 57 through 71. ... A nanowire is a wire of dimensions of the order of a nanometer (10−9 meters). ...

The compound Fe(COT)₂, when refluxed in toluene with dimethylsulfoxide and Dimethoxyethane for 5 days, is found to form magnetite and crystalline carbon also containing carbon nanotubes ^[8] Toluene, also known as methylbenzene or phenylmethane is a clear, water-insoluble liquid with the typical smell of paint thinners, redolent of the sweet smell of the related compound benzene. ... Dimethyl Sulfoxide (DMSO, empirically C2H6OS), also known as methyl sulfoxide or sulfinylbismethane, is a chemical compound. ... Dimethoxyethane, also known as glyme, monoglyme, dimethyl glycol, ethylene glycol dimethyl ether, dimethyl cellosolve, and DME, is a clear, colorless, and liquid ether that is used as a solvent. ... // Headline text Magnetite is a ferrimagnetic mineral form of iron(II,III) oxide, with chemical formula Fe3O4, one of several iron oxides and a member of the spinel group. ... 3D model of three types of single-walled carbon nanotubes. ...

Because COT changes conformation between tub-shaped and planar with addition or subtraction of electrons, it could, in principle, be used to construct artificial muscles. Such devices have been contemplated to be makeable by grafting COT derivatives to a backbone of a suitable conducting polymer, which would supply or remove the reducing equivalents ^[9]. Almost all organic polymers are electrical insulators. ...

See also

• Cyclobutadiene
• Semibullvalene is an isomer.
• Willstatter synthesis

Cyclobutadiene is the smallest [n]-annulene ([4]-annulene), an extremely unstable hydrocarbon having a lifetime shorter than five seconds in the free state. ...

References

The Journal of the American Chemical Society (usually abbreviated as , or JACS), is a peer-reviewed scientific journal, published since 1879 by the American Chemical Society. ... A digital object identifier (or DOI) is a standard for persistently identifying a piece of intellectual property on a digital network and associating it with related data, the metadata, in a structured extensible way. ...

External links

• Links to external chemical sources