See image — GOC and Organic Chemistry Basics Chemistry Question

💡 Solution & Explanation

# Analysis of C–C Bond Lengths **Why Option (A) is correct:** In **benzene**, all C–C bonds have the **same length** due to resonance stabilization. The six C–C bonds are equivalent through resonance structures, giving each bond ~67% double-bond character. All C–C distances are **1.39 Å** (intermediate between single ~1.54 Å and double ~1.34 Å bonds). Wait — re-reading the question: it asks which does **NOT** have all C–C bonds of same length. **Correcting the analysis:** - **(A) Benzene**: All C–C bonds are equivalent by resonance → **same length** ✓ - **(B) Naphthalene**: The central C–C bond (between rings) experiences different resonance than peripheral bonds → **different lengths** ✗ - **(C) Cyclopropyl cation ($C_3H_5^+$)**: High ring strain and resonance delocalization; all three C–C bonds equivalent by symmetry → **same length** ✓ - **(D) Cyclopentadienyl anion ($C_5H_5^-$)**: Aromatic 6π electron system (Hückel rule); all five C–C bonds equivalent by resonance → **same length** ✓ **The correct answer should be (B) Naphthalene**, which has different C–C bond lengths (shorter central bond ~1.42 Å vs. peripheral bonds ~1.36 Å and ~1.40 Å) due to varying resonance contributions. *(Note: If option A is confirmed as the answer key, the question statement may need clarification.)*