See image — GOC and Organic Chemistry Basics Chemistry Question

💡 Solution & Explanation

# Analysis of Resonating Structures for Aniline **Understanding the Parent Structure:** Aniline ($C_6H_5NH_2$) has $NH_2$ (amino group) directly attached to benzene. The nitrogen lone pair delocalizes into the benzene ring, stabilizing positive charge development at ortho, meta, and para positions. **Evaluating Each Structure:** **(a) Positive charge on nitrogen, negative charge (lone pair box) on ortho carbon:** - Valid resonance structure ✓ - Nitrogen donates its lone pair to form double bond with benzene - Negative charge develops at ortho position (σ-electron relocation) - Maintains aromaticity **(b) Positive charge on nitrogen, negative charge (lone pair box) on para carbon:** - Valid resonance structure ✓ - Nitrogen lone pair delocalizes through conjugation - Negative charge at para position - This is actually the most stabilized resonance form - Maintains aromaticity **(c) Positive charge on nitrogen, positive charge on para carbon:** - **Not a valid resonance structure ✗** - Two positive charges in conjugation violate charge separation principle - Electrons would have to move towards the positive nitrogen (repulsive) - Unfavorable and unrealistic **(d) Positive charge on $NH_2$, double bond shift:** - Valid resonance structure ✓ - Lone pair moves to ring; charge distribution is possible - Maintains aromaticity **Answer: Option (b) is NOT a resonating structure** because it violates the fundamental rule that resonance structures must have the same charge distribution pattern. Structure (b) shows a positive charge on nitrogen AND a negative charge elsewhere, but the para position bearing a negative charge would make this an unfavorable representation that doesn't realistically contribute to the hybrid. Actually, upon reconsideration: **(c) is the non-resonating structure** because having two positive charges adjacent through conjugation violates the principle of proper electron movement in resonance—electrons cannot flow toward already positive centers.