See image — GOC and Organic Chemistry Basics Chemistry Question

💡 Solution & Explanation

# Solution: Basicity Order of Anilines **Key Concept:** The basicity of anilines depends on electron density at the nitrogen atom. Electron-donating groups increase basicity; electron-withdrawing groups decrease basicity. **Analysis of each compound:** 1. **$C_6H_5-NH_2$ (aniline):** No substituent — baseline basicity (moderate) 2. **$o-NO_2-C_6H_4-NH_2$:** $NO_2$ is strongly electron-withdrawing. At ortho position, it causes steric hindrance AND electronic withdrawal, severely reducing basicity. 3. **$m-NO_2-C_6H_4-NH_2$:** $NO_2$ at meta position is electron-withdrawing through resonance, but less effective than ortho due to no steric hindrance. Basicity reduced moderately. 4. **$p-NO_2-C_6H_4-NH_2$:** $NO_2$ at para position is most effective at withdrawing electrons by resonance (direct conjugation with benzene ring), maximizing the reduction in basicity. **Basicity Order:** $$\text{(1)} > \text{(3)} > \text{(2)} > \text{(4)}$$ - Aniline is most basic (unsubstituted) - Meta-nitro is more basic than ortho (less steric hindrance) - Para-nitro is least basic (maximum resonance withdrawal) **Answer: (D)**