Cubane 417665 216084488 2008-05-31T00:29:07Z Thijs!bot 1392310 robot Adding: [[ko:쿠반]] {{Chembox new | Name = '''Cubane''' | ImageFileL1 = Cuban.svg | ImageSizeL1 = 120px | ImageNameL1 = Structural formula of cubane | ImageFileR1 = Cubane-3D-balls.png | ImageSizeR1 = 120px | ImageNameR1 = Ball-and-stick model of cubane | IUPACName = Cubane<ref>According to page 41 of [http://www.iupac.org/reports/provisional/abstract04/BB-prs310305/Chapter2-Sec20-24.pdf a 2004 IUPAC guide], cubane is the "preferred IUPAC name."</ref> | OtherNames = Pentacyclo[4.2.0.0<sup>2,5</sup>.0<sup>3,8</sup>.0<sup>4,7</sup>]octane | Section1 = {{Chembox Identifiers | CASNo = 277-10-1 | SMILES = C12C3C4C1C5C4C3C25 | InChI=1/C8H8/c1-2-5-3(1)<br />7-4(1)6(2)8(5)7/h1-8H }} | Section2 = {{Chembox Properties | Formula = C<sub>8</sub>H<sub>8</sub> | MolarMass = 104.15 g/mol | Density = 1.29 g/cm<sup>3</sup> | MeltingPt = 131 °C}} }} '''Cubane''' (C<sub>8</sub>H<sub>8</sub>) is a synthetic [[hydrocarbon]] [[molecule]] that consists of eight [[carbon]] [[atom]]s arranged at the corners of a [[Cube (geometry)|cube]], with one [[hydrogen]] atom attached to each carbon molecule. It is one of the [[Platonic hydrocarbons]]. Cubane is a solid [[crystal]]line substance. The cubane molecule was first synthesized in [[1964]] by Dr. [[Philip Eaton]], a professor of chemistry at the [[University of Chicago]].<ref name="eaton-1964">''Cubane'' Philip E. Eaton and Thomas W. Cole [[J. Am. Chem. Soc.]]; '''1964'''; 86(15) pp 3157 - 3158; {{DOI|10.1021/ja01069a041}}.</ref> Before its synthesis, researchers believed that cubic carbon-based molecules could only exist in theory. It was believed that cubane would be impossible to synthesize because the unusually sharp 90-degree bonding angle of the carbon atoms would be too highly [[strain (chemistry)|strained]] and hence unstable. Surprisingly, once formed, cubane is actually quite kinetically stable due to a lack of readily available decomposition paths. Cubane and its derivative compounds have many important properties. The 90-degree bonding angle of the carbon atoms in cubane means that the bonds are highly strained. Therefore, cubane compounds are highly reactive, which in principle may make them useful as high-density, high-energy [[fuel]]s and [[explosive]]s for example [[octanitrocubane]] and [[heptanitrocubane]]. Cubane also has the highest density of any hydrocarbon, further contributing to its ability to store large amounts of energy. Researchers are looking into using cubane and similarly synthesized cubic molecules in [[medicine]] and [[nanotechnology]]. ==Synthesis== The original 1964 cubane [[organic synthesis]] is a classic and starts from ''2-cyclopentenone'' (compound '''1.1''' in ''scheme 1'')<ref name="eaton-1964"/><ref>''The Cubane System'' Philip E. Eaton and Thomas W. Cole [[J. Am. Chem. Soc.]]; '''1964'''; 86(5) pp 962 - 964; {{DOI|10.1021/ja01059a072}}</ref>: :[[Image:CubaneSynthesisPrecursor.png|500px|Scheme 1. Synthesis of cubane precursor bromocyclopentadienone]] Reaction with [[N-Bromosuccinimide|''N''-bromosuccinimide]] in [[Carbon tetrachloride]] places an [[allylic]] bromine atom in '''1.2''' and further [[bromination]] with [[bromine]] in [[pentane]] - [[methylene chloride]] gives the tribromide '''1.3'''. Two equivalents of [[hydrogen bromide]] are [[elimination reaction|eliminated]] from this compound with [[diethylamine]] in [[diethyl ether]] to ''bromocyclopentadienone'' '''1.4''' :[[Image:CubaneSynthesis.png|500px|Scheme 2. Synthesis of cubane 1964]] In the second part (''scheme 2''), the spontaneous [[Diels-Alder reaction|Diels-Alder dimerization]] of '''2.1''' to '''2.2''' is akin the dimerization of [[cyclopentadiene]] to [[dicyclopentadiene]]. For the next steps to succeed only the [[endo isomer]] should form which it does because the bromine atoms on their approach take up positions as far away from each other and the carbonyl group as possible. In this way the like-dipole interactions are minimized in the [[transition state]] for this reaction step. Both [[carbonyl]] groups are [[protecting group|protected]] as [[acetal]]s with [[ethylene glycol]] and [[P-Toluenesulfonic acid|''p''-toluenesulfonic acid]] in [[benzene]] and then one of them is selectively deprotected with aqueous [[hydrochloric acid]] to '''2.3''' In the next step endo isomer '''2.3''' with both [[alkene]] groups in close proximity forms the cage-like isomer '''2.4''' in a [[photochemical]] [2+2] [[cycloaddition]]. The [[haloketone|bromoketone]] group is converted to ring-contracted [[carboxylic acid]] '''2.5''' in a [[Favorskii rearrangement]] with [[potassium hydroxide]]. Next the thermal [[decarboxylation]] takes place through the [[acid chloride]] (with [[thionyl chloride]]) and the [[tert-butyl]] [[perester]] '''2.6''' (with [[t-butyl hydroperoxide]] and [[pyridine]]) to '''2.7'''. then the acetal is once more removed in '''2.8''', another Favorskii rearrangement gives '''2.9''' and finally another decarboxylation '''2.10''' and '''2.11'''. ==Inorganic cubes and related derivatives== The cube motif occurs outside of the area of organic chemistry. Prevalent non-organic cubes are the [Fe<sub>4</sub>-S<sub>4</sub>] clusters found pervasively [[iron-sulfur protein]]s. Such species contain sulfur and Fe at alternating corners. Alternatively such inorganic cube clusters can often be viewed as interpenetrated S<sub>4</sub> and Fe<sub>4</sub> tetrahedra. Many organometallic compounds adopt cube structures, examples being ([[cyclopentadienyl|Cp]]Fe)<sub>4</sub>(CO)<sub>4</sub>, ([[pentamethylcyclopentadienyl|Cp*]]Ru)<sub>4</sub>Cl<sub>4</sub>, and ([[triphenylphosphine|Ph<sub>3</sub>P]]Ag)<sub>4</sub>I<sub>4</sub>, ==Reactions== [[Cuneane]] may be produced from cubane by [[metal-ion-catalyzed σ-bond rearrangement]]. <ref>Michael B. Smith, Jerry March, ''March’s Advanced Organic Chemistry'', 5 th Ed., John Wiley & Sons, Inc., 2001, p. 1459. ISBN 0-471-58589-0</ref> <ref>K. Kindler, K. Lührs, ''Chem. Ber.'', vol. 99, 1966, p. 227.</ref> ==References== {{Reflist}} ==External links== * [http://www.ch.ic.ac.uk/local/projects/b_muir/Cubane/Cubanepro/Reactivity.html cubane chemistry at Imperial College London] * [http://www.compchemwiki.org/index.php?title=Cubane Computational Chemistry Wiki] [[Category:Hydrocarbons]] [[de:Cuban]] [[fr:Cubane]] [[ko:쿠반]] [[it:Cubano]] [[ja:キュバン]] [[pl:Kuban]] [[pt:Cubano (hidrocarboneto)]] [[fi:Kubaani]] [[zh:立方烷]]