Cyclotetradecaheptaene, often referred to as [14]annulene, is a hydrocarbon with molecular formula C14H14, which played an important role in the development of criteria (Hückel's rule) for aromaticity, a stabilizing property of central importance in physical organic chemistry. It forms dark-red needle-like crystals.[1]
Although the conjugated ring of [14]annulene contains 4n+2 electrons, it only exhibits limited evidence for being aromatic. It does not fully conform to Hückel's rule because none of its cis/trans isomers can adopt a completely planar conformation due to crowding of the interior hydrogens.[2] There is evidence that it has two isomeric forms of comparable stability (trans, cis, trans, cis, trans, trans, cis- with four interior hydrogens (shown in the infobox) and trans, cis, trans, cis, trans, cis, cis- with three interior hydrogens) which rapidly interconvert at room temperature but can be observed at low temperature by NMR.[3] Its 1H NMR spectrum shows evidence of aromatic ring currents that result in an upfield shift for the interior hydrogens. In contrast, the corresponding [12]- and [16]annulenes, which are weakly antiaromatic or nonaromatic, have downfield shifted interior hydrogens. However, unlike the undoubtedly aromatic [18]annulene, [14]annulene does not bear the hallmark aromatic property of chemical stability, and it quickly decomposes when exposed to light and air.[4]
Referencesedit
^ abChiang, Chian C.; Paul, Iain C. (1972). "Crystal and Molecular Structure of [14]Annulene". J. Am. Chem. Soc.94 (13): 4741–4743. doi:10.1021/ja00768a058.
^G. M. Badger. Aromatic Character and Aromaticity. Cambridge University Press. p. 96.
^H., Lowry, Thomas (1987). Mechanism and theory in organic chemistry. Richardson, Kathleen Schueller. (3rd ed.). New York: Harper & Row. ISBN0060440848. OCLC 14214254.{{cite book}}: CS1 maint: multiple names: authors list (link)
^Sondheimer, Franz; Gaoni, Yehiel (1960). "Unsaturated Macrocyclic Compounds. XV. Cyclotetradecaheptaene". Journal of the American Chemical Society. 82 (21): 5765–5766. doi:10.1021/ja01506a061.
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cyclotetradecaheptaene, often, referred, annulene, hydrocarbon, with, molecular, formula, c14h14, which, played, important, role, development, criteria, hückel, rule, aromaticity, stabilizing, property, central, importance, physical, organic, chemistry, forms,. Cyclotetradecaheptaene often referred to as 14 annulene is a hydrocarbon with molecular formula C14H14 which played an important role in the development of criteria Huckel s rule for aromaticity a stabilizing property of central importance in physical organic chemistry It forms dark red needle like crystals 1 Cyclotetradecaheptaene NamesIUPAC name 1E 3Z 5E 7Z 9E 11E 13Z cyclotetradeca 1 3 5 7 9 11 13 heptaeneOther names 14 AnnuleneIdentifiersCAS Number 2873 14 5 Y3D model JSmol Interactive imageChEBI CHEBI 37523 YChemSpider 10160742 YPubChem CID 11988275CompTox Dashboard EPA DTXSID20475276InChI InChI 1S C14H14 c1 2 4 6 8 10 12 14 13 11 9 7 5 3 1 h1 14H b2 1 3 1 4 2 5 3 6 4 7 5 8 6 9 7 10 8 11 9 12 10 13 11 14 12 14 13 YKey RYQWRHUSMUEYST ILUIUFOYSA N YSMILES C1C CC CC CC CC CC CC 1PropertiesChemical formula C 14H 14Molar mass 182 266 g mol 1Appearance dark red needle like crytalsSolubility in water InsolubleSolubility in benzene SolubleStructure 1 Crystal structure monoclinicSpace group P21 c No 14Lattice constant a 8 640 A b 4 376 A c 14 997 Aa 90 b 106 g 90 Formula units Z 2 molecules per cellHazardsOccupational safety and health OHS OSH Main hazards Flammable reactiveExcept where otherwise noted data are given for materials in their standard state at 25 C 77 F 100 kPa Y verify what is Y N Infobox referencesStructure and aromaticity editAlthough the conjugated ring of 14 annulene contains 4n 2 electrons it only exhibits limited evidence for being aromatic It does not fully conform to Huckel s rule because none of its cis trans isomers can adopt a completely planar conformation due to crowding of the interior hydrogens 2 There is evidence that it has two isomeric forms of comparable stability trans cis trans cis trans trans cis with four interior hydrogens shown in the infobox and trans cis trans cis trans cis cis with three interior hydrogens which rapidly interconvert at room temperature but can be observed at low temperature by NMR 3 Its 1H NMR spectrum shows evidence of aromatic ring currents that result in an upfield shift for the interior hydrogens In contrast the corresponding 12 and 16 annulenes which are weakly antiaromatic or nonaromatic have downfield shifted interior hydrogens However unlike the undoubtedly aromatic 18 annulene 14 annulene does not bear the hallmark aromatic property of chemical stability and it quickly decomposes when exposed to light and air 4 References edit a b Chiang Chian C Paul Iain C 1972 Crystal and Molecular Structure of 14 Annulene J Am Chem Soc 94 13 4741 4743 doi 10 1021 ja00768a058 G M Badger Aromatic Character and Aromaticity Cambridge University Press p 96 H Lowry Thomas 1987 Mechanism and theory in organic chemistry Richardson Kathleen Schueller 3rd ed New York Harper amp Row ISBN 0060440848 OCLC 14214254 a href Template Cite book html title Template Cite book cite book a CS1 maint multiple names authors list link Sondheimer Franz Gaoni Yehiel 1960 Unsaturated Macrocyclic Compounds XV Cyclotetradecaheptaene Journal of the American Chemical Society 82 21 5765 5766 doi 10 1021 ja01506a061 nbsp This article about a hydrocarbon is a stub You can help Wikipedia by expanding it vte Retrieved from https en wikipedia org w index php title Cyclotetradecaheptaene amp oldid 1179641871, wikipedia, wiki, book, books, library,
