See image — GOC and Organic Chemistry Basics Chemistry Question

💡 Solution & Explanation

# Steric Inhibition of Resonance **Concept:** Steric inhibition of resonance occurs when bulky groups attached to an atom prevent the orbital alignment needed for resonance stabilization. **Analysis for each option:** **(A)** Isopropyl group ortho to $N(CH_3)_2$ - Large isopropyl creates severe steric clash with the dimethylamino group - Prevents $N$ lone pair from overlapping with benzene π-system - Strong steric inhibition ✓ **(B)** Methyl groups ortho and para to $N(CH_3)_2$ - Methyl groups are small; minimal steric hindrance - Allows resonance to proceed **(C)** Two methyl groups meta to $N(CH_3)_2$ - Meta positions are **far from the nitrogen atom** - Do **not directly interfere** with $N$ lone pair orbital alignment - Minimal steric inhibition of resonance with the amino group **(D)** Two tert-butyl groups ortho and para to $N(CH_3)_2$ - Very bulky tert-butyl groups in ortho positions - Severe steric clashing prevents resonance **Why (C) is correct:** The question asks where steric inhibition is **NOT expected**. In option (C), the methyl substituents are positioned meta to the electron-donating amino group. Since meta positions don't create steric clashes with the $N$-attached lone pair orbital, resonance between nitrogen and the benzene ring remains **unobstructed**. The answer is **(C)** — steric inhibition of resonance **cannot** occur here due to the meta-positioning of the methyl groups.