See image — GOC and Organic Chemistry Basics Chemistry Question

💡 Solution & Explanation

# Analysis of Base Strength **Key Principle:** Base strength of amines depends on the availability of lone pair electrons on nitrogen for protonation. **Evaluation of each compound:** **(A) Aniline (Phenyl amine):** $C_6H_5-NH_2$ - The nitrogen lone pair is *delocalized* into the benzene ring's π-system through resonance - This reduces electron density on N, making it a **weak base** **(B) Cyclohexylamine:** $C_6H_{11}-NH_2$ - Saturated cycloalkyl group is **purely electron-donating** (alkyl group effect) - No resonance delocalization occurs - Lone pair on N remains **highly available** for protonation - **Strongest base** **(C) Methylaniline (Toluidine):** $CH_3-C_6H_4-NH_2$ - Still contains the benzene ring attached to nitrogen - Resonance delocalization of lone pair into aromatic ring still occurs (though methyl is weakly donating) - Weaker than (B) **(D) N-formylaniline:** $C_6H_5-NH-COCH_3$ - Lone pair on N is involved in amide resonance with $C=O$ - Electron density on N is further reduced - **Weakest base** **Answer: (B)** — Cyclohexylamine is the strongest base because the saturated alkyl group activates the lone pair through inductive donation without competing resonance effects that would delocalize electron density away from nitrogen.