See image — GOC and Organic Chemistry Basics Chemistry Question

💡 Solution & Explanation

# Analysis of Electron-Donation Power (Resonance Effects) **Key Principle:** Electron-donating power in resonance is determined by the ability to donate electron density through the double bond to stabilize an adjacent positive charge. **Evaluating Each Group:** **Group I: $-CH=CH_2$ (Vinyl group)** - Alkene is weakly electron-donating through resonance - C=C can donate electrons, but effect is modest - **Moderate donor** **Group II: $-CH=CH-OCH_3$** - Oxygen (highly electronegative) is strongly electron-donating - $OCH_3$ donates electrons through resonance: $O$ lone pair → double bond → conjugated system - This activates the entire conjugated system - **Strong donor** (oxygen's strong +M effect dominates) **Group III: $-CH=CH-NO_2$** - $NO_2$ is a powerful electron-withdrawing group (strong −M effect) - Withdraws electrons from the conjugated system - Deactivates resonance donation - **Weak/negative donor** **Resonance Order of Electron-Donation Power:** $$II > I > III$$ **Why (C) is correct:** The $OCH_3$ group (II) has the strongest resonance donation ability due to oxygen's electronegativity and lone pair donation. The vinyl group (I) provides moderate donation. The $NO_2$ group (III) is electron-withdrawing and actively opposes donation. **Why others are wrong:** - (A) & (B) incorrectly place III as a strong donor - (D) incorrectly places III before I