See image — GOC and Organic Chemistry Basics Chemistry Question

💡 Solution & Explanation

# Acidity Order Analysis **Key Principle:** Phenolic acidity is enhanced by electron-withdrawing groups and reduced by electron-donating groups on the benzene ring. ## Step-by-Step Analysis: **Compound I:** 2,6-Dimethylphenol - Two methyl groups ($-CH_3$) are electron-donating (activating) - **Decreases acidity** through inductive donation **Compound II:** 2,4,6-Trimethylphenol - Three methyl groups ($-CH_3$) donate electrons - **More electron donation than I** → **Lower acidity than I** **Compound III:** 2,6-Dimethyl-4-nitrophenol - Two methyl groups donate electrons (activating) - One $-NO_2$ group withdraws electrons (deactivating) - The $-NO_2$ group is para to the $-OH$, providing strong electron withdrawal - **Net effect:** Withdrawal dominates → **Increases acidity significantly** **Compound IV:** 2,4,6-Trimethyl-3-nitrophenol - Three methyl groups donate electrons - One $-NO_2$ group withdraws electrons (meta position to $-OH$) - Meta-nitro is **less effective** at withdrawal than para-nitro - **Lower acidity than III** due to more methyl groups and weaker nitro positioning ## Acidity Order: $$\text{II} < \text{I} < \text{IV} < \text{III}$$ **Explanation:** IV < III because the para-nitro in III is more effective at electron withdrawal than the meta-nitro in IV, even though IV has an extra methyl group. **Answer: (D) $\mathbf{I < II < IV < III}$** ✓