Corannulene

• - circulene
• Dibenzo [ ghi, mno ] fluoranthene

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Corannulene, even - circulene and dibenzo [ ghi, mno ] fluoranthene called, is the smallest known and successfully synthesized representatives of the [n ] - Circulene. It was first produced in 1966 by Barth and Lawton in a remarkable, 16 - step synthesis with classical methods.

Structure

Corannulene consists of five fused benzene rings that form a central pentagon and can thus be considered as the smallest fragment of fullerene ( C60), which still has its characteristic curvature. This structural property "forces" the molecule to take the best possible compromise between delocalization and voltage. Before the structure was unambiguously confirmed by X-ray structural analysis, the prediction if it has a planar or curved structure was difficult. Hanson and Nordmann showed that Corannulene a curved, shell-like structure with C5v symmetry ( see point groups ) has.

The molecule shows a quick bowl inversion, the energy barrier was measured at Corannulenderivaten by NMR experiments ( at -64 ° C) to 42.7 kJ / mol ( 10.2 kcal / mol ) ( 200,000 inversions per second). The standard enthalpy of ΔHf0 is 463.7 kJ / mol and was determined by bomb calorimetry.

The bowl depth ( from the central five-membered ring, and are clamped by the edge of the ten carbon atoms ) is defined by the distance between the two planes is 87 pm.