| Revision as of 20:44, 4 May 2011 editWikitanvirBot (talk | contribs)144,145 editsm r2.7.1) (robot Adding: pt:Kekuleno← Previous edit |
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{{chembox |
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| Verifiedfields = changed |
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| verifiedrevid = 409052197 |
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| Watchedfields = changed |
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| ImageFile = kekulene.svg |
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| verifiedrevid = 427467941 |
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| ImageSize = 200px |
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| ImageFileL1 = kekulene.svg |
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| ImageName = Skeletal formula |
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| ImageSizeL1 = 140px |
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| ImageFile1 = Kekulene-3D-balls.png |
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| ImageAlt = Skeletal formula of kekulene |
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| ImageSize1 = 220px |
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| ImageFileR1 = Kekulene 3D spacefill.png |
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| ImageName1 = Ball-and-stick model |
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| ImageSizeR1= 140px |
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| IUPACName = |
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| ImageAlt1 = Space-filling model of the kekulene molecule |
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| OtherNames = <nowiki></nowiki>–Coronaphen |
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| PIN = 15,23:16,22-Di(metheno)naphthotetraphenopentaphene |
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| OtherNames = <nowiki></nowiki>–Coronaphen, <nowiki></nowiki>] |
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|Section1={{Chembox Identifiers |
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|Section1={{Chembox Identifiers |
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| Abbreviations = |
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| Abbreviations = |
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| CASNo_Ref = {{cascite|correct|??}} |
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| CASNo=15123-47-4 |
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| CASNo=15123-47-4 |
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| PubChem = 5460755 |
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| PubChem = 5460755 |
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| SMILES=C1=CC2=CC3=C4C=C2C5=CC6=C(C=CC7=CC8=C(C=C76)C9=CC2=C(C=CC6=C2C=C2C(=C6) |
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C=CC6=C2C=C4C(=C6)C=C3)C=C9C=C8)C=C51 |
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| SMILES = C1=CC2=CC3=C4C=C2C5=CC6=C(C=CC7=CC8=C(C=C76)C9=CC2=C(C=CC6=C2C=C2C(=C6)C=CC6=C2C=C4C(=C6)C=C3)C=C9C=C8)C=C51 |
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| ChemSpiderID_Ref = {{chemspidercite|changed|chemspider}} |
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| ChemSpiderID = 4574217 |
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| InChI = 1/C48H24/c1-2-26-14-28-5-6-30-16-32-9-10-34-18-36-12-11-35-17-33-8-7-31-15-29-4-3-27-13-25(1)37-19-39(27)41(29)21-43(31)45(33)23-47(35)48(36)24-46(34)44(32)22-42(30)40(28)20-38(26)37/h1-24H |
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| InChIKey = TYPKKLUFDMGLAC-UHFFFAOYAP |
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| StdInChI_Ref = {{stdinchicite|changed|chemspider}} |
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| StdInChI = 1S/C48H24/c1-2-26-14-28-5-6-30-16-32-9-10-34-18-36-12-11-35-17-33-8-7-31-15-29-4-3-27-13-25(1)37-19-39(27)41(29)21-43(31)45(33)23-47(35)48(36)24-46(34)44(32)22-42(30)40(28)20-38(26)37/h1-24H |
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| StdInChIKey_Ref = {{stdinchicite|changed|chemspider}} |
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| StdInChIKey = TYPKKLUFDMGLAC-UHFFFAOYSA-N |
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| RTECS = |
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| MeSHName = |
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| ChEBI_Ref = {{ebicite|changed|EBI}} |
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| ChEBI = 32987 |
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|Section2={{Chembox Properties |
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|Section2={{Chembox Properties |
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| C=48|H=24 |
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| C=48 | H=24 |
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| Appearance= |
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| Appearance= |
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| Density=1.46 g/cm<sup>3</sup> (calc.)<ref name=str/> |
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| Density= |
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| MeltingPt= |
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| Solubility= |
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|Section3={{Chembox Hazards |
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| Section3 = {{Chembox Structure |
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| Structure_ref =<ref name=str>{{cite journal|doi=10.1002/cber.19831161022 |title=Cycloarenes, a New Class of Aromatic Compounds, II. Molecular Structure and Spectroscopic Properties of Kekulene |date=1983 |last1=Staab |first1=Heinz A. |last2=Diederich |first2=François |last3=Krieger |first3=Claus |last4=Schweitzer |first4=Dieter |journal=Chemische Berichte |volume=116 |issue=10 |pages=3504–3512 }}</ref> |
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| MainHazards= |
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| CrystalStruct = |
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| FlashPt= |
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| SpaceGroup = ], C2/c |
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| Autoignition= |
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| PointGroup = |
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| LattConst_a = 2795.1(4) pm |
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| LattConst_b = 457.9(1) pm |
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| LattConst_c = 2268.0(2) pm |
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| LattConst_alpha = |
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| LattConst_beta = 109.64(1) |
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| LattConst_gamma = |
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| LattConst_ref = |
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| LattConst_Comment = |
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| UnitCellVolume = |
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| UnitCellFormulas = 4 |
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| Coordination = |
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| MolShape = |
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| OrbitalHybridisation = |
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| Dipole = |
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|Section8={{Chembox Hazards |
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| FlashPt= |
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'''Kekulene''' is a ] with the chemical formula C<sub>48</sub>H<sub>24</sub>. It was first synthesized in 1978, and was named in honor of ], the discoverer of the structure of the ] molecule. |
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'''Kekulene''' is a ] which consists of 12 fused benzene rings arranged in a circle. It is therefore classified as a -] with the chemical formula C<sub>48</sub>H<sub>24</sub>. It was first synthesized in 1978,<ref>{{cite journal |last1=Staab |first1=Heinz A. |last2=Diederich |first2=François |title=Cycloarenes, a New Class of Aromatic Compounds, I. Synthesis of Kekulene |journal=Chemische Berichte |date=October 1983 |volume=116 |issue=10 |pages=3487–3503 |doi=10.1002/cber.19831161021}}</ref> and was named in honor of ], the discoverer of the structure of the ] molecule. |
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== Geometry and electronic structure == |
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The nature of the ] within the molecule was long debated, as several distinctly different arrangements were possible. The two most significant proposals are the "Clar" configuration, consisting of six ]-like (aromatic 6 π-electron) rings connected by bridging bonds and ]s in non-aromatic rings, and the "Kekulé" configuration, consisting of two concentric aromatic rings (18 π-electron inner, 30 π-electron outer) linked by radial single bonds.<ref name="Krieger1979">{{cite journal |last1=Krieger |first1=Claus |last2=Diederich |first2=Francois |last3=Schweitzer |first3=Dieter |last4=Staab |first4=Heinz A. |title=Molecular Structure and Spectroscopic Properties of Kekulene |journal=Angewandte Chemie International Edition in English |date=September 1979 |volume=18 |issue=9 |pages=699–701 |doi=10.1002/anie.197906991|url=http://elib.uni-stuttgart.de/handle/11682/7566 }}</ref><ref>{{cite journal |last1=Aihara |first1=Junichi |title=Is superaromaticity a fact or an artifact? The kekulene problem |journal=Journal of the American Chemical Society |date=January 1992 |volume=114 |issue=3 |pages=865–868 |doi=10.1021/ja00029a009}}</ref><ref name="Diederich1978">{{cite journal |last1=Diederich |first1=François |last2=Staab |first2=Heinz A. |title=Benzenoidversus Annulenoid Aromaticity: Synthesis and Properties of Kekulene |journal=Angewandte Chemie International Edition in English |date=May 1978 |volume=17 |issue=5 |pages=372–374 |doi=10.1002/anie.197803721}}</ref><ref>{{cite journal |last1=Jiao |first1=Haijun |last2=Schleyer |first2=Paul von Ragué |title=Is Kekulene Really Superaromatic? |journal=Angewandte Chemie International Edition in English |date=1 November 1996 |volume=35 |issue=20 |pages=2383–2386 |doi=10.1002/anie.199623831}}</ref><ref>{{cite journal |last1=Schweitzer |first1=D. |last2=Hausser |first2=K.H. |last3=Vogler |first3=H. |last4=Diederich |first4=F. |last5=Staab |first5=H.A. |title=Electronic properties of kekulene |journal=Molecular Physics |date=11 August 2006 |volume=46 |issue=5 |pages=1141–1153 |doi=10.1080/00268978200101861|url=http://elib.uni-stuttgart.de/handle/11682/7578 }}</ref><ref>{{cite journal |last1=Staab |first1=Heinz A. |last2=Diederich |first2=FrançOis |last3=Krieger |first3=Claus |last4=Schweitzer |first4=Dieter |title=Cycloarenes, a New Class of Aromatic Compounds, II. Molecular Structure and Spectroscopic Properties of Kekulene |journal=Chemische Berichte |date=October 1983 |volume=116 |issue=10 |pages=3504–3512 |doi=10.1002/cber.19831161022}}</ref><ref>{{cite journal |last1=Zhou |first1=Zhongxiang |title=Are kekulene, coronene, and corannulene tetraanion superaromatic? Theoretical examination using hardness indices |journal=Journal of Physical Organic Chemistry |date=February 1995 |volume=8 |issue=2 |pages=103–107 |doi=10.1002/poc.610080209}}</ref> |
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<gallery caption="Proposed electronic configurations" mode="packed"> |
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File:Kekulene (kekule conjugation).png|"Kekulé" configuration: Two concentric aromatic rings |
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File:Kekulene (linked benzenes).png|"Clar" configuration: Benzene rings alternating with non-aromatic linkers |
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</gallery> |
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The synthesis of the compound, first reported in 1978,<ref name="Diederich1978"/> allowed experimental determination of the electronic structure. In the late 1970s, ] provided evidence of benzene rings<ref name="Diederich1978"/> and X-ray analysis determined that the structure had had alternating aromatic and non-aromatic rings,<ref name="Krieger1979"/> both consistent with the Clar configuration. In 2019, the configuration was determined to be one consisting of benzene-like rings alternating with non-aromatic linkages, by using single molecule ] to measure the carbon–carbon bond-lengths and ]s.<ref name="Iago2019">{{cite journal |last1=Pozo |first1=Iago |last2=Majzik |first2=Zsolt |last3=Pavliček |first3=Niko |last4=Melle-Franco |first4=Manuel |last5=Guitián |first5=Enrique |last6=Peña |first6=Diego |last7=Gross |first7=Leo |last8=Pérez |first8=Dolores |title=Revisiting Kekulene: Synthesis and Single-Molecule Imaging |journal=Journal of the American Chemical Society |date=17 September 2019 |volume=141 |issue=39 |pages=15488–15493 |doi=10.1021/jacs.9b07926|pmid=31525873 |pmc=6786662 |doi-access=free }}</ref> This configuration is in keeping with ], as it has the largest number of disjoint aromatic π sextets. |
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Though the whole structure is essentially planar, it only has three-fold symmetry rather than six-fold. The carbon–hydrogen bonds in the center of the ring have a slight alternating tilt out of the plane to avoid ] among the hydrogen atoms.<ref name="Iago2019"/> |
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==References== |
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==References== |
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{{Reflist}} |
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*{{cite journal | last1 = Peter | first1 = R. | last2 = Jenny | first2 = W. | title = 250. Höhere, kondensierte Ringsysteme. 1. Mitteilung : Untersuchungen in der -Coronaphenreihe: Synthese von Di- | journal = Helvetica Chimica Acta | volume = 49 | pages = 2123 | year = 1966 | doi = 10.1002/hlca.660490717}} |
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*{{cite journal | doi = 10.1002/cber.19831161021 | title = Cycloarenes, a New Class of Aromatic Compounds, I. Synthesis of Kekulene | year = 1983 | last1 = Staab | first1 = Heinz A. | authorlink1=Heinz Staab| last2 = Diederich | first2 = François | journal = Chemische Berichte | volume = 116 | pages = 3487}} |
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*{{cite journal | doi = 10.1002/anie.197906991 | title = Molecular Structure and Spectroscopic Properties of Kekulene | year = 1979 | last1 = Krieger | first1 = Claus | last2 = Diederich | first2 = Francois | last3 = Schweitzer | first3 = Dieter | last4 = Staab | first4 = Heinz A. | journal = Angewandte Chemie International Edition in English | volume = 18 | pages = 699}} |
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*{{cite journal | doi = 10.1021/ja00029a009 | title = Is superaromaticity a fact or an artifact? The kekulene problem | year = 1992 | last1 = Aihara | first1 = Junichi | journal = Journal of the American Chemical Society | volume = 114 | pages = 865}} |
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*{{cite journal | doi = 10.1002/anie.197803721 | title = Benzenoidversus Annulenoid Aromaticity: Synthesis and Properties of Kekulene | year = 1978 | last1 = Diederich | first1 = François | last2 = Staab | first2 = Heinz A. | journal = Angewandte Chemie International Edition in English | volume = 17 | pages = 372}} |
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*{{cite journal | doi = 10.1002/anie.199623831 | title = Is Kekulene Really Superaromatic? | year = 1996 | last1 = Jiao | first1 = Haijun | last2 = Schleyer | first2 = Paul von Ragué | authorlink2 =Paul von Ragué Schleyer| journal = Angewandte Chemie International Edition in English | volume = 35 | pages = 2383}} |
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*{{cite journal | doi = 10.1080/00268978200101861 | title = Electronic properties of kekulene | year = 1982 | last1 = Schweitzer | first1 = D. | last2 = Hausser | first2 = K.H. | last3 = Vogler | first3 = H. | last4 = Diederich | first4 = F. | last5 = Staab | first5 = H.A. | journal = Molecular Physics | volume = 46 | pages = 1141 }} |
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*{{cite journal | doi = 10.1021/ja00004a005 | title = Is superbenzene superaromatic? | year = 1991 | last1 = Cioslowski | first1 = Jerzy | last2 = O'Connor | first2 = Peter B. | last3 = Fleischmann | first3 = Eugene D. | journal = Journal of the American Chemical Society | volume = 113 | pages = 1086}} |
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*{{cite journal | doi = 10.1002/cber.19831161022 | title = Cycloarenes, a New Class of Aromatic Compounds, II. Molecular Structure and Spectroscopic Properties of Kekulene | year = 1983 | last1 = Staab | first1 = Heinz A. | last2 = Diederich | first2 = FrançOis | last3 = Krieger | first3 = Claus | last4 = Schweitzer | first4 = Dieter | journal = Chemische Berichte | volume = 116 | pages = 3504}} |
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*{{cite journal | doi = 10.1002/poc.610080209 | title = Are kekulene, coronene, and corannulene tetraanion superaromatic? Theoretical examination using hardness indices | year = 1995 | last1 = Zhou | first1 = Zhongxiang | journal = Journal of Physical Organic Chemistry | volume = 8 | pages = 103}} |
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