See image — GOC and Organic Chemistry Basics Chemistry Question

💡 Solution & Explanation

# Analysis of Resonating Structures **Resonating (resonance) structures** must satisfy: 1. Same atomic connectivity (skeleton) 2. Different electron distribution 3. Movement of electrons (π or lone pairs) only --- ## Checking Each Option: **(A)** $H-C \equiv N^{\oplus}$ and $H-C = N^{\ominus}H$ - Same atoms, same connectivity ✓ - Electron movement between triple/double bond ✓ - **Valid resonance pair** ✗ **(B)** $CH_3CH = CHCH_3$ and $CH_3CH_2CH = CH_2$ - First structure: C₄ chain with one double bond at position 2-3 - Second structure: C₄ chain with one double bond at position 3-4 - **Different atomic connectivity** (double bond location differs) - Electrons shifted, but atoms rearranged → **Not resonance** - This represents different isomers, not resonance structures ✓ **(C)** Enolate resonance pair - Oxygen anion lone pair ↔ carbanion at CH - Same skeleton, electron rearrangement ✓ - **Valid resonance pair** ✗ **(D)** Benzene and its cation radical - Same carbon skeleton with different electron distributions ✓ - **Valid resonance pair** ✗ --- **Answer: (B)** is correct because the two structures have **different skeletal connectivity** (double bond at different positions), making them structural isomers rather than resonance structures.