The following hydrocarbon has an unusually large dipole moment. Explain how a large dipole moment might arise.

The given hydrocarbon is aromatic. One ring will getpositive and the other negatively charged. Due to charge separation between oppositely charged rings; the large dipole moment arises. Both rings are aromatic because both have 6 pi electrons and hence follows Huckel rule 4n+2 pi electrons where n is

In this, the positive ring compound is an aromatic tropylium ion with 6 pi electrons. In this case, there are several resonances, forms that delocalize the positive charge around the seven-membered ring.

In the case of the negative ring compound which is an aromatic cyclopentadienyl anion with 6 pi electrons, In this case, there are several resonance forms that delocalize the negative charge around the five-membered ring.

Positive and negative charge delocalization

Both rings are aromatic with charge separation