Double Aromaticity in the 3,5-Dehydrophenyl Cation and in Cyclo[6]carbon

Schleyer, Paul VR and Jiao, Haijun and Glukhovtsev, Mikhail N and Chandrasekhar, Jayaraman and Kraka, Elfi (1994) Double Aromaticity in the 3,5-Dehydrophenyl Cation and in Cyclo[6]carbon. In: Journal of the American Chemical Society, 116 (22). 10129-10134 .

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Abstract

The presence of two (4n+2)-electron conjugated systems in perpendicular planes results in considerable aromatic stabilization. Despite having two fewer hydrogens, the 6 pi e-2 sigma e 3,5-dehydrophenyl cation (C6H3+, 1) is 32.7 (CCSD(T)/6-31G**) and 35.2 kcal/mol (RMP4sdtq/6-3iG*//RMP2(fu)/6-31G*) more stable than the phenyl cation (evaluated by an isodesmic reaction involving benzene and m-dehydrobenzene (4)). Cation 1, the global C6H3+ minimum, is 11.7,24.2, 11.8, and 30.4 kcal/mol lower in energy than the 2,6- (11) and 3,4-dehydrophenyl (12) cations as well as the open-chain isomers 13 and 14 (RMP4sdtq/6-31G*//RMP2(fu)/6-31G* + ZPE(RMP2(fu)/6-31G*)). The stability of 1 is increased hyperconjugatively by 2,4,6-trisilyl substitution. The double aromaticity of 1 is indicated by the computed magnetic susceptibility exaltations (IGLO/II//RMP2(fu)/6-31G*) of -5.2, -6.8, -15, and -23.2 relative to 11, 12, 13, and 14, respectively. Thus, 1 fulfills the geometric, energetic, and magnetic criteria of aromaticity. The double aromaticity of the D-6h cyclo[6]carbon is apparent from the same criteria

Item Type:	Journal Article
Publication:	Journal of the American Chemical Society
Publisher:	American Chemical Society
Additional Information:	Copyright of this article belongs to American Chemical Society.
Department/Centre:	Division of Chemical Sciences > Organic Chemistry
Date Deposited:	01 Jun 2011 06:48
Last Modified:	01 Jun 2011 06:48
URI:	http://eprints.iisc.ac.in/id/eprint/36418

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