The stable, cyclic cyclopentadienyl anion () acts as a classic aromatic electron system. How many to — Hydrocarbons Chemistry Question

💡 Solution & Explanation

The cyclopentadienyl anion ring contains 5 carbon atoms. Two localized double bonds in the parent cyclopentadiene initially contribute 4 $\pi$ electrons. The carbon bearing the negative charge exists in an $sp^2$ hybridized state, placing its remaining lone pair of electrons into an unhybridized $p$ -orbital that perfectly aligns with the adjacent $\pi$ system. This specific lone pair contributes exactly 2 electrons to complete the $4n+2=6$ aromatic octet.