Corannules
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Surname | Corannules | ||||||||||||
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Molecular formula | C 20 H 10 | ||||||||||||
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properties | |||||||||||||
Molar mass | 250,30 g · mol -1 | ||||||||||||
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As far as possible and customary, SI units are used. Unless otherwise noted, the data given apply to standard conditions . |
Corannulene , also known as [5] -circulene and dibenzo [ ghi, mno ] fluoranthene , is the smallest known and successfully synthesized representative of the [ n ] -circulene . It was first prepared in 1966 by Barth and Lawton in a remarkable 16-step synthesis using classical methods.
structure
Corannulene consists of five fused benzene rings that form a central pentagon and can therefore be regarded as the smallest fragment of fullerene (C 60 ), which still has its characteristic curvature. This structural property “forces” the molecule to make the best possible compromise between delocalization and tension . Before the structure was clearly confirmed by X-ray diffraction analysis, it was difficult to predict whether it was planar or domed. Hanson and Nordmann showed that corannulene a curved, cup-like structure with C 5v - symmetry (see point groups has).
The molecule shows a rapid shell inversion, the energy barrier of which on corannulene derivatives was measured by NMR experiments (at −64 ° C) to be 42.7 kJ / mol (10.2 kcal / mol) (approx. 200,000 inversions per second). The standard enthalpy of formation Δ H f 0 is 463.7 kJ / mol and was determined by means of bomb calorimetry .
The shell depth, which is defined by the distance between the two levels (which are spanned by the central five-membered ring and the ten carbon atoms of the edge), is 87 pm .
Individual evidence
- ↑ This substance has either not yet been classified with regard to its hazardousness or a reliable and citable source has not yet been found.
- ^ WE Barth, RG Lawton: Dibenzo [ghi, mno] fluoranthene , in J. Am. Chem. Soc. 88. 1966, pp. 380-381; doi : 10.1021 / ja00954a049 .
- ^ WE Barth, RG Lawton: The Synthesis of Corannulene , in: J. Am. Chem. Soc. 93. 1971, pp. 1730-1745; doi : 10.1021 / ja00736a028 .