See image — GOC and Organic Chemistry Basics Chemistry Question

💡 Solution & Explanation

# Solution: Strongest Base Among Aniline Derivatives **Key Principle:** Base strength depends on the availability of the lone pair on nitrogen. Electron-donating groups increase basicity; electron-withdrawing groups decrease it. **Analysis of each option:** **(1) Aniline ($C_6H_5-NH_2$):** The benzene ring is directly attached to $NH_2$. The aromatic ring withdraws electron density through resonance (the lone pair delocalizes into the $\pi$ system), reducing basicity. **(2) N-Methylaniline ($C_6H_5-NH-CH_3$):** Still has the electron-withdrawing benzene ring directly attached, making it weaker than option (3). **(3) o-Toluidine/2-Methylaniline:** The $CH_3$ group is on the benzene ring (ortho to $NH_2$), not directly attached to nitrogen. The $CH_3$ is an electron-donating alkyl group that increases electron density on the ring through inductive effect. This *strengthens* the $N-H$ bond's basicity without significant resonance withdrawal. **(4) Benzylamine ($C_6H_5-CH_2-NH_2$):** Although the $CH_2$ spacer somewhat isolates the nitrogen from the ring's resonance withdrawal, the overall effect is weaker than having a direct electron-donating substituent on the ring. **Answer: Option (3)** is the strongest base because the methyl group directly attached to the benzene ring donates electron density, enhancing the basicity of the amine, while the $CH_2$ spacer in option (4) and the direct ring attachment in options (1) and (2) are less favorable.