See image — GOC and Organic Chemistry Basics Chemistry Question

💡 Solution & Explanation

# Analyzing Base Strength of Aniline Derivatives **Key Principle:** Base strength depends on nitrogen's electron density. Electron-donating groups increase basicity; electron-withdrawing groups decrease it. **Analysis of each option:** **(A) $C_6H_5NH_2$ (Aniline)** - Benzene ring is directly attached to $NH_2$ - Resonance effect: lone pair on N delocalizes into the aromatic ring, reducing basicity **(B) $p-NO_2-C_6H_4NH_2$ (p-Nitroaniline)** - $NO_2$ is a strong electron-withdrawing group - Further reduces electron density on N through resonance and inductive effects - **Very weak base** **(C) $m-NO_2-C_6H_4NH_2$ (m-Nitroaniline)** - $NO_2$ is meta to $NH_2$ (less effective resonance withdrawal) - Still weakens the base, but less than para isomer **(D) $C_6H_5CH_2NH_2$ (Benzylamine)** - $NH_2$ is attached to an **aliphatic carbon** ($-CH_2-$), not directly to benzene - The saturated $CH_2$ acts as a **sigma spacer**, preventing resonance delocalization - Nitrogen retains maximum electron density - **Strongest base** **Conclusion:** Option **(D)** is the strongest base because the $CH_2$ group isolates the amino group from the benzene ring's resonance effects, allowing the lone pair to remain available for protonation.