1,6-Methano(10)annulene

bracket 1,6-Methano[10]annulene 1,6-Methano[10]annulene 1,6-methanonaphthalene.svg 150px Bicyclo[4.4.1]undeca-1,3,5,7,9-pentaene 2443-46-1 correct FDA HMG3LPN8YP 137603 121264 c1ccc2ccccc(c1)C2 1/C11H10/c1-2-6-11-8-4-3-7-10(5-1)9-11/h1-8H,9H2 OORRQYZWSVJKSO-UHFFFAOYAC 1S/C11H10/c1-2-6-11-8-4-3-7-10(5-1)9-11/h1-8H,9H2 OORRQYZWSVJKSO-UHFFFAOYSA-N 11 10 1,6-Methano[10]annulene (also known as 1,6-methanonaphthalene or homonaphthalene) is an aromatic hydrocarbon with chemical formula C11H10. It was the first stable aromatic compound based on the cyclodecapentaene system to be discovered. Preparation The classical organic synthesis of this compound starts with Birch reduction of naphthalene to isotetralin, which adds dichlorocarbene (prepared in situ from chloroform and potassium tert-butoxide) to form a transannular cyclopropane ring. A second reduction then removes the chloride substituents. Finally, 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) oxidation removes the central transannular bond and dehydrogenates unto aromaticity. alt=synthetic route to 1,6-methanonapthalene|center|750x750px Aromaticity It is analogous to cyclodecapentaene ([10]annulene), but with two hydrogen atoms replaced by a transannular methylene bridge (\sCH2\s). Consequently, it obeys Hückel's rule (n = 2) and despite the distortion from planarity introduced by the methylene bridge, the compound is aromatic. In fact, when prepared by Vogel in the 1960s it was the first stable aromatic cyclodecapentaene to be discovered. Its aromaticity is confirmed by two main pieces of evidence. Firstly, the similarity in carbon-carbon bond lengths as measured by x-ray crystallography is inconsistent with alternating single and double bonds. The actual structure is better considered as a pair of resonance hybrids (like the Kekulé structures of benzene) rather than as having alternating single and double bonds. Secondly, its 1H NMR spectrum displays influence of the diamagnetic ring current which is characteristic of aromatic compounds. The peripheral protons around the ring are deshielded while the methylene bridge nuclei are strongly shielded. Its resonance energy is smaller than that of naphthalene. Possible applications Homonaphthalene has been used in the production of conductive polymers.Peart Patricia A. Repka Lindsay M. Tovar John D. May 2008 Emerging Prospects for Unusual Aromaticity in Organic Electronic Materials: The Case for Methano[10]annulene https://onlinelibrary.wiley.com/doi/10.1002/ejoc.200701102 European Journal of Organic Chemistry en 2008 13 2193–2206 10.1002/ejoc.200701102 1434-193X subscription See also Homoaromaticity Cyclodecapentaene 1,5-Methano[10]annulene References Applications of Topological Methods in Molecular Chemistry Remi Chauvin Christine Lepetit Bernard Silvi Esmail Alikhani Springer International Publishing 2016 9783319290225 22 Challenges and Advances in Computational Chemistry and Physics Carlo Gatti Ahmed M. Orlando Emanuele Monza Leonardo Lo Presti 10.1007/978-3-319-29022-5_5 101–129 Exploring Chemistry Through the Source Function for the Electron and the Electron Spin Densities Forfeiture of the aromaticity of a bridged [10]annulene by benzannelation Richard K. Hill Carolyn B. Giberson James V. Silverton J. Am. Chem. Soc. 1988 110 2 497–500 10.1021/ja00210a031 1,6-Methano[10]annulene 6 731 54 11 10.15227/orgsyn.054.0011 Emanuel Vogel W. Klug A. Breuer http://www.orgsyn.org/demo.aspx?prep=cv6p0731 Roth Wolfgang R. Manfred Böhm Resonance Energy of Bridged [10]Annulene Angew. Chem. Int. Ed. 1983 22 12 1007–1008 10.1002/anie.198310071 Vogel Emanuel H. D. Roth The Cyclodecapentaene System Angew. Chem. Int. Ed. 1964 3 3 228–229 10.1002/anie.196402282 Vogel Emanuel W. A. Böll Angew. Chem. Int. Ed. Substitution of 1,6-Methanocyclodecapentaene 1964 3 9 642 10.1002/anie.196406421 Category:Aromatic hydrocarbons Category:Non-benzenoid aromatic carbocycles