Question

Cyclopentadiene is non-aromatic. Postively charged ion of cyclopentadiene is anti-aromatic whereas negative charged ion of cyclopentadiene is aromatic. Explain.

Answer 1

The cycloheptatrienyl anion has 8 electrons, and thecycloheptatrienyl cation has 6 electrons. Therefore the cycloheptatrienyl anion (4N, N=2) is antiaromatic (if it were to stay planar), and the cycloheptatrienyl cation (4N+2, N=1) is aromatic.