Cyclododecahexaene or [12]annulene (C 12H 12) is a member of the series of annulenes with some interest in organic chemistry with regard to the study of aromaticity.[1] Cyclododecahexaene is non-aromatic due to the lack of planarity of the structure.[citation needed] On the other hand the dianion with 14 electrons is a Hückel aromat and more stable.
According to in silico experiments the tri-trans isomer is expected to be the most stable, followed by the 1,7-ditrans and the all cis-isomers (+1 kcal/mol) and by the 1,5-ditrans isomer (+5 kcal/mol).
The first [12]annulene with sym-tri-trans configuration was synthesized in 1970 from a tricyclic precursor by photolysis at low temperatures. On heating the compound rearranges to a bicyclic [6.4.0] isomer. Reducing the compound at low temperatures allowed analysis of the dianion by proton NMR with the inner protons resonating at -4.5 ppm relative to TMS, evidence of an aromaticdiamagnetic ring current.[2]
[12]annulene synthesis
In one study the 1,7-ditrans isomer is generated at low temperatures in THF by dehydrohalogenation of a hexabromocyclododecane with potassium tert-butoxide. Reduction of this compound at low temperature with caesium metal leads first to the radical anion and then to the dianion. The chemical shift for the internal protons in this compound is with +0.2 ppm much more modest than in the tri-trans isomer.
[12]annulene synthesis
Heating the radical ion solution to room temperature leads to loss of one equivalent of hydrogen and formation of the heptalene radical anion.
Referencesedit
^Kiesewetter, Matthew K.; Gard, Matthew N.; Reiter, Richard C.; Stevenson, Cheryl D. (2006). "Reactions Involving Di-trans-[12]Annulenes". Journal of the American Chemical Society. 128 (49): 15618–15624. doi:10.1021/ja062846u. PMID 17147369.
^Oth, J. F. M.; Schröder, G. (1971). "Annulenes. Part XII. The dianion of [12]annulene". J. Chem. Soc. B: 904–907. doi:10.1039/j29710000904. ISSN 0045-6470.
November 10, 2023
cyclododecahexaene, this, article, needs, additional, citations, verification, please, help, improve, this, article, adding, citations, reliable, sources, unsourced, material, challenged, removed, find, sources, news, newspapers, books, scholar, jstor, august,. This article needs additional citations for verification Please help improve this article by adding citations to reliable sources Unsourced material may be challenged and removed Find sources Cyclododecahexaene news newspapers books scholar JSTOR August 2011 Learn how and when to remove this template message Cyclododecahexaene or 12 annulene C12 H12 is a member of the series of annulenes with some interest in organic chemistry with regard to the study of aromaticity 1 Cyclododecahexaene is non aromatic due to the lack of planarity of the structure citation needed On the other hand the dianion with 14 electrons is a Huckel aromat and more stable Cyclododecahexaene Tri trans isomer of cyclododecahexaeneNamesIUPAC name 1 3 5 7 9 11 CyclododecahexaeneOther names 12 annuleneIdentifiersCAS Number 3227 77 8 Y3D model JSmol Interactive imageEZEZEZEZ Interactive imageChemSpider 57559573EZEZEZEZ 10381705PubChem CID 53438306InChI InChI 1S C12H12 c1 2 4 6 8 10 12 11 9 7 5 3 1 h1 12HKey KWULAWFQRPFWEH UHFFFAOYSA NEZEZEZEZ InChI 1S C12H12 c1 2 4 6 8 10 12 11 9 7 5 3 1 h1 12H b2 1 3 1 4 2 5 3 6 4 7 5 8 6 9 7 10 8 11 9 12 10 12 11 Key KWULAWFQRPFWEH FWEBNODZSA NSMILES C1 CC CC CC CC CC C1EZEZEZEZ C 1 C C C C C C C C C C C1PropertiesChemical formula C 12H 12Molar mass 156 228 g mol 1Except where otherwise noted data are given for materials in their standard state at 25 C 77 F 100 kPa Infobox references According to in silico experiments the tri trans isomer is expected to be the most stable followed by the 1 7 ditrans and the all cis isomers 1 kcal mol and by the 1 5 ditrans isomer 5 kcal mol The first 12 annulene with sym tri trans configuration was synthesized in 1970 from a tricyclic precursor by photolysis at low temperatures On heating the compound rearranges to a bicyclic 6 4 0 isomer Reducing the compound at low temperatures allowed analysis of the dianion by proton NMR with the inner protons resonating at 4 5 ppm relative to TMS evidence of an aromatic diamagnetic ring current 2 12 annulene synthesisIn one study the 1 7 ditrans isomer is generated at low temperatures in THF by dehydrohalogenation of a hexabromocyclododecane with potassium tert butoxide Reduction of this compound at low temperature with caesium metal leads first to the radical anion and then to the dianion The chemical shift for the internal protons in this compound is with 0 2 ppm much more modest than in the tri trans isomer 12 annulene synthesisHeating the radical ion solution to room temperature leads to loss of one equivalent of hydrogen and formation of the heptalene radical anion References edit Kiesewetter Matthew K Gard Matthew N Reiter Richard C Stevenson Cheryl D 2006 Reactions Involving Di trans 12 Annulenes Journal of the American Chemical Society 128 49 15618 15624 doi 10 1021 ja062846u PMID 17147369 Oth J F M Schroder G 1971 Annulenes Part XII The dianion of 12 annulene J Chem Soc B 904 907 doi 10 1039 j29710000904 ISSN 0045 6470 Retrieved from https en wikipedia org w index php title Cyclododecahexaene amp oldid 1158222707, wikipedia, wiki, book, books, library,
