Question:
Which one of the following is aromatic?
Which one of the following is aromatic?
Show Hint
The tropylium ion (C\(_7\)H\(_7^+\)) is a classic example of an aromatic carbocation with 6 \(\pi\)-electrons.
Updated On: Apr 16, 2026
- Cycloheptatrienyl cation
- Cycloheptatriene
- Cyclooctatetraene
- Cyclopentadienyl cation
Show Solution
Verified By Collegedunia
The Correct Option is A
Solution and Explanation
Step 1: Understanding the Concept:
Hückel's rule states that a planar, cyclic, conjugated system with (4n+2) \(\pi\)-electrons is aromatic.
Step 2: Detailed Explanation:
• (A) Cycloheptatrienyl cation (tropylium ion): C\(_7\)H\(_7^+\). It has 6 \(\pi\)-electrons (4n+2, n=1), is planar and cyclic, and is aromatic. • (B) Cycloheptatriene: Non-aromatic (not fully conjugated, has a CH\(_2\) group). • (C) Cyclooctatetraene: 8 \(\pi\)-electrons, tub-shaped (non-planar) to avoid antiaromaticity, so non-aromatic. • (D) Cyclopentadienyl cation: C\(_5\)H\(_5^+\). It has 4 \(\pi\)-electrons (4n, n=1), would be antiaromatic if planar, so it is non-aromatic and unstable.
Step 3: Final Answer:
Cycloheptatrienyl cation is aromatic, which corresponds to option (A).
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