1. Cyclooctatetraene(COT) 1.1 Chemical properties

• IUPAC-name: Cycloocta-1,3,5,7-tetraene

• Trivial name: [8] , COT

• Formula: C8H8

• : 104,15 g mol-1

• Density: 0,93 g ml-1

• : -5 bis -3 °C

• Boiling point: 142-143 °C

• Physical state: liquid

• Appearance: colourless to slightly yellow

1.2 Structure

Figure 1: Structure of COT.

Cyclooctatetraene is an unsaturated . It is a cyclical system consisting of 8 carbon atoms with four alternating single and double bonds, which implies that it has two distinct C-C bond lengths. This has been proven by X-Ray diffraction data. Cycloocta-1,3,5,7-tetraene adopts a non-planar, energy efficient tub conformation. This and the fact that it cannot fulfill the Hückel rule means that it is not an . A proof for that is that it is subject to usual reactions of double bonds, i.e. electrophilic addition instead of more aromatic reactions like substitutions.

Seite 1 1.3 Synthesis Cycloocta-1,3,5,7-tetraene was originally synthesized in 1905 in munich by Richard Willstäter. He used pseudopelletierin, which is won from the pomgrenade tree as the educt and modified it in a 6 step synthesis. The first step of the synthesis is an elimination, where a H2O molecule is demerged. Subsequently, a Hofmann- elemination takes place, which serves to generate the second of four double bonds. It also severs the first bond of the amine to the ring. This exact reaction, using methyl iodide and silver oxide, repeats and the third double bond is manufactured. To generate the fourth double bond 1, 3, 5 – Cyclooctatriene undergoes an addition reaction, in which Brom is added in 1, 6, Position. This is additionally prefered because it keeps the conjugated π -system. This electrophillic addition has an Allyl- as its transition state. The next step is a nucleophilic substitution, where both previously added brom-atoms are exchanged for a Dimethylamine each. Due to the existance of two new dimethylamine groups, it is possible to eliminate them using the same reaction, the Hofmann-elimination, to get the third and fourth double bond in the molecule.[1]

Figure 1: Presentation of the synthesis of COT.[2]

Another possibility of synthesizing COT, which doesn't include a naturally occuring substance as a reagant, was established by Reppe. He used the multiply . A polymerization reaction with catalytic usage of nickel cyanide and under extreme circumstances takes place.

Seite 2 Figure 2: Reaction equation of the synthesis by Reppe.[2]

1.4 Usage Currently cyclooctatetraen does not have many known applications. However, its anion can be used to produce so called organometallic sandwich compounds. A known organometallic compound is Fe(COT)2. If this compound is solved in ,

DMSO and Dimethoxyethane and refluxed for five days, carbon nanotubes start to form. As of yet, the application fields are mostly theoretical, however, they are a big matter of discussion and research.[5]

Furthermore, one dimensional EU-COT sandwich compounds can officiate as nanowires, which are being used in electronic devices.

In a reaction with water and mercury sulfate as a catalyst Phenylacetaldehyd can be won out of Cycloocta-1,3,5,7-tetraen, which with hypochlorous acid reacts to Terephtaldialdehyd. The aldehyd can then be oxidated to Terephtalacid, which in turn is actually important in the chemical industry.[3]

2. Source

[1] Richard Willstäter und Ernst Waser, Über Cyclo-Tetraen, Berichte der chemisch deutschen Gesellschaft Band 44, 1911, S.3423 ff. [2] www.wikipedia.org/wiki/Cyclooctatetraen. [3] www.spektrum.de/lexikon/chemie/cyclooctatetraen/2153. [4] Prof. Nakajima, JST Nanostructed Materials Project, 19.2.2008. [5] Walter, Erich C.; Beetz, Tobias; sfeir, Matthew Y., Brus Louis E; Steigerwald, Michael L, Crystalline Graphite from an Organometallic Solution Phase Reaction; 2006.

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