Structure of 4,4?,6,6?-tetranitro-2,2?-dicarboxybiphenyl dimethyl ester

Popova, E. G.; Chetkina, L. A.; Соболев, А. Н.

doi:10.1007/bf00745768

Cited by 1 publication

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“…AM1 calculations show discrete C 2 and C 1 conformations for this molecule, with the observed C 1 structure disfavored by 2.6 kcal/mol. However, the dimethyl ester of 4,4‘,6,6‘-tetranitro-2,2‘-diphenic acid as well as 6,6‘-dinitro-2,2‘-diphenic acid, display undistorted, more nearly symmetric structures, so the observed preference for a higher energy C 1 conformation by solid 4,4‘,6,6‘-tetranitro-2,2‘-diphenic acid is likely to be the result of packing forces.…”

Section: Resultsmentioning

confidence: 99%

Polyphenylbiphenyls and Polyphenylfluorenes

Tong

Lau

et al. 1998

J. Am. Chem. Soc.

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A series of highly congested polyphenylbiphenyls and polyarylfluorenes has been prepared and their X-ray structures determined. Decaphenylbiphenyl adopts a very unusual C 1 -symmetric geometry (rather than the more intuitive D 2 geometry) in which one of the central benzene rings is distorted into a boat conformation. AM1 calculations confirm that the C 1 geometry is the ground state but indicate that less highly substituted biphenyls should adopt D 2 geometries. The structure of 2,2′,4,4′,6,6′-hexaphenylbiphenyl supports the latter prediction; this material has crystallographic C 2 symmetry and (except for the orientation of the para phenyl groups) approximate D 2 symmetry in the solid state. Octaphenylfluorenone has been prepared in four steps from tetraphenylcyclopentadienone. Its X-ray structure shows the fluorenone core to be twisted and sterically shielded by the eight peripheral phenyl groups; nevertheless, phenylmagnesium bromide adds easily to the carbonyl group of its equally hindered dimethyl derivative, 2, 3,5,6,7,8-hexaphenyl-1,4-di(p-tolyl)fluorenone. Reduction of the resulting fluorenol with TiCl 3 gives a nonaarylfluorene, 2,3,5,6,7,8,9-heptaphenyl-1,4-di(p-tolyl)fluorene, and its X-ray structure shows distortions similar to those of octaphenylfluorenone.

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Section: Resultsmentioning

confidence: 99%