Which of the following specific chemical species are correctly classified as aromatic according to H — GOC and Organic Chemistry Basics Chemistry Question

💡 Solution & Explanation

Tropylium cation (6 $\pi$ e-, n=1), Cyclopentadienyl anion (6 $\pi$ e-, n=1), and Cyclopropenyl cation (2 $\pi$ e-, n=0) are all cyclic, planar, fully conjugated, and obey the $4n+2$ rule. The Cyclopentadienyl cation has 4 $\pi$ e- and is highly unstable and anti-aromatic.