See image — GOC and Organic Chemistry Basics Chemistry Question

💡 Solution & Explanation

# Solution: Acidity Order of Substituted Phenols **Key Principle:** Phenol acidity depends on the stability of the conjugate base (phenoxide ion). Electron-withdrawing groups stabilize the negative charge; electron-donating groups destabilize it. **Analysis of each substituent:** | Compound | Substituent | Effect | Acidity | |----------|-------------|--------|---------| | **III** | $-NO_2$ (electron-withdrawing) | Strongly stabilizes $O^-$ via resonance & induction | **Most acidic** | | **I** | $-Cl$ (weakly electron-withdrawing) | Moderately stabilizes $O^-$ via induction | **More acidic** | | **II** | $-CH_3$ (electron-donating) | Destabilizes $O^-$ | **Less acidic** | | **IV** | $-OCH_3$ (strongly electron-donating) | Strongly destabilizes $O^-$ via resonance & induction | **Least acidic** | **Reasoning:** - $NO_2$ is highly electronegative and withdraws electrons through both inductive and resonance effects, making the conjugate base most stable - $Cl$ is less electronegative; only inductive withdrawal occurs - $CH_3$ and $OCH_3$ are donating groups that reduce the stability of the phenoxide anion - $OCH_3$ is more donating than $CH_3$ due to oxygen's higher electronegativity allowing better resonance donation **Answer: (B) III > I > II > IV** ✓ This order correctly reflects decreasing acidity based on conjugate base stability.