Question

22) Hexahelicene, an aromatic compound, seems to be a poor candidate for optical activity because all of its atoms are sp2 hybridized and presumably flat. This compound has a very high calue for its specific rotation, la p= 3700. Explam wy hexahelicene is optically active.

Answer 1

Hexahelicene exists in two enantiomeric forms because of over- crowding, which affects the end two rings. The congestion is relieved by part of one of the end rings taking a position above the other so that the molecule starts to resemble the thread of a screw or helix.

Despite of having all carbons sp2 hybridised Its not actually Flat structure,End two rings of hexahelicene due to crowding take a position one above the other, in this form hexahelicene lacks a plane of symmetry and thus optically active.Its example of chirality without stereogenic carbon.

This ring plane is above the to rest of the ring 1- This ring is below the plane to sext at the rings Hexhelicane