The descending order of basicity of following amines is : Choose the correct answer from the options given below :
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When comparing the basicity of amines, consider whether they are aliphatic or aromatic. For aliphatic amines, more alkyl groups generally increase basicity. For aromatic amines, the presence and nature of substituents on the ring significantly affect basicity. Electron-donating groups increase basicity, while electron-withdrawing groups decrease it.
To rank the basicity of the provided amines in descending order, analyze substituent electronic effects and amine structure.
Aromatic amines exhibit lower basicity than aliphatic amines. This is because the lone pair on the nitrogen atom in aromatic amines is delocalized into the aromatic ring, reducing its availability for protonation.
The methoxy substituent (—OCH3) in compound (B) is electron-donating. It elevates electron density on the nitrogen, rendering compound (B) more basic than aromatic amines lacking such electron-donating groups.
The nitro substituent (—NO2) in compound (C) is a potent electron-withdrawing group. It substantially diminishes basicity by withdrawing electron density from both the ring and the nitrogen atom.
Dimethylamine (E) is an aliphatic amine and is typically more basic. This is due to the direct availability of the nitrogen atom's lone pair for protonation, which is unaffected by resonance.
Methylamine (D) is also an aliphatic amine and is generally more basic than aromatic amines.
Based on these principles, the amines can be arranged in descending order of basicity:
