See image — GOC and Organic Chemistry Basics Chemistry Question

💡 Solution & Explanation

# Electron-Withdrawing Power in Resonance **Understanding Resonance Effect (R-effect):** The electron-withdrawing power through resonance depends on the ability of a group to withdraw electron density from an attached benzene ring via $\pi$-conjugation. **Analyzing Each Group:** **I. $-CHO$ (Aldehyde):** - Strong electron-withdrawing group - Carbonyl carbon is highly electrophilic and strongly accepts electrons through resonance - Withdraws electron density: $\pi$ electrons from benzene flow toward the C=O **II. $-\mathbf{COOCH_3}$ (Ester):** - Electron-withdrawing but less than aldehyde - Oxygen atoms can donate electrons, reducing the withdrawing effect - Resonance structures show partial electron donation from both oxygens (competing effects) **III. $-\mathbf{CONH_2}$ (Amide):** - Weak electron-withdrawing group - The $NH_2$ group is strongly electron-donating through resonance - Nitrogen donates its lone pair into the C=O, significantly reducing the withdrawing power - More electron-donating than electron-withdrawing overall **Resonance Order:** $$\text{Aldehyde} > \text{Ester} > \text{Amide}$$ $$\boxed{\text{I} > \text{II} > \text{III}}$$ **Answer: (A)** The aldehyde has the strongest R-effect (no competing donors), the ester is intermediate, and the amide's amino group heavily donates electrons, making it the weakest electron-withdrawer.