Question

Which of the following compound is aromatic?

• A. Cyclopropenyl cation
• B. Cyclobutadiene
• C. Cyclopentadienyl cation
• D. Cycloheptatrienyl anion
• E. Cyclooctatetraene

Hint:

Chemistry Tip: Small charged rings like cyclopropenyl cation are classic aromatic examples with $2\pi$ electrons.

Answer 1

The Correct Option is A

Concept:
A compound is aromatic if it satisfies all conditions:

• Cyclic
• Planar
• Fully conjugated
• Contains $(4n+2)\pi$ electrons (Hückel rule)

If it has $4n\pi$ electrons and planar conjugation, it is antiaromatic.
Step 1: Check option (A): Cyclopropenyl cation}}
Three-membered ring with one positive charge. It has: $$2\pi \text{ electrons}$$ Since: $$2 = 4n+2 \quad (n=0)$$ It satisfies Hückel rule. Hence aromatic.
Step 2: Check remaining options briefly.

• Cyclobutadiene: $4\pi$ electrons $\Rightarrow$ antiaromatic.
• Cyclopentadienyl cation: $4\pi$ electrons $\Rightarrow$ antiaromatic.
• Cycloheptatrienyl anion: $8\pi$ electrons $\Rightarrow$ antiaromatic/nonplanar.
• Cyclooctatetraene: $8\pi$ electrons but nonplanar, non-aromatic.

Step 3: Final answer.
Only aromatic compound among given options is: $$\boxed{\text{Cyclopropenyl cation}}$$ Hence correct option is (A). :contentReference[oaicite:1]{index=1}