See image — GOC and Organic Chemistry Basics Chemistry Question

💡 Solution & Explanation

# Analysis of Resonating Structures **Understanding Equivalent Resonance Structures:** Resonance structures must have: - Identical molecular formula - Same connectivity of atoms - Only electrons shifting between positions - All atoms in the same spatial arrangement --- **Evaluating Each Option:** **(A) $HCOO^-$ (Formate ion)** $$\text{Structure 1: } H-C(=O)-O^- \quad \longleftrightarrow \quad \text{Structure 2: } H-C(-O^-)=O$$ ✓ **Valid resonance pair:** Only electron density shifts between the two oxygen atoms while maintaining C-O single and double bond character. The negative charge delocalizes over both oxygens. **(B) $CH_2=CH-CH=CH_2$ (1,3-butadiene)** - This has conjugated double bonds but the structures shown don't represent true resonance (would require breaking σ bonds) - Not equivalent resonance structures **(C) Aniline ($C_6H_5NH_2$ with one double bond shown)** - The double bond position in the ring changes with different resonance structures - Represents aromatic resonance, but structures are not simply "equivalent" in the traditional sense **(D) Cyclohexene with aldehyde** - No resonance is possible; this is a fixed structure - The aldehyde and ring double bond cannot interchange electrons meaningfully --- **Answer: (A)** The formate ion $HCOO^-$ is the only system where electron pairs can delocalize between two oxygen atoms through the central carbon, creating two equivalent resonance structures with the same connectivity.