Question

Cycloheptatrienyl cation is

• A. non-benzenoid and non-aromatic
• B. non-benzenoid and aromatic
• C. benzenoid and non-aromatic
• D. benzenoid and aromatic
• E. non-benzenoid and anti-aromatic

Hint:

Aromaticity shortcut: - 6, 10, 14 π electrons → aromatic - 4, 8, 12 π electrons → anti-aromatic Tropylium ion (C\textsubscript{7}H\textsubscript{7}\textsuperscript{+}) is a classic aromatic species

Answer 1

The Correct Option is B

Concept: Aromaticity (Hückel's Rule) A compound is aromatic if:
• Cyclic and planar
• Fully conjugated
• Contains \( (4n + 2) \) π electrons Cycloheptatrienyl cation (tropylium ion): Structure:
• 7-membered ring
• 3 double bonds → 6 π electrons
• Positive charge contributes to conjugation

Step 1: Check π electrons \[ \text{π electrons} = 6 \] \[ 6 = 4n + 2 \quad (n=1) \]

Step 2: Conjugation
• All carbons are \(sp^2\)
• Continuous overlap → conjugated system

Step 3: Planarity
• Structure is planar → allows delocalization Conclusion:
• Satisfies all aromaticity conditions
• Not benzene-like → non-benzenoid Hence: \[ \text{Non-benzenoid and aromatic} \]