Amines and Amides: Basicity and the Nitrogen Functional Groups
A nitrogen lone pair makes an amine basic and nucleophilic, and how available that pair is explains why some amines are far stronger bases than others. Acylating one gives an amide, the bond that later holds proteins and many polymers together.
What a learner can do afterwards
- Rank primary, secondary and aromatic amines by base strength and justify the order
- Give a route from a haloalkane or a nitrile to an amine and say why the product can react further
- Write the formation of an amide from an acyl chloride and an amine, and explain why the amide is not basic
1 · Read
Picture ammonia with hydrogens swapped for carbon groups. One swap gives a primary amine, two give a secondary amine, three give a tertiary amine. Every amine carries one nitrogen lone pair, and that pair does two jobs: it grabs a proton, so the amine is a base, and it attacks electron-poor carbon, so the amine is a nucleophile. The fishy smell of old fish is trimethylamine escaping.
Base strength is really a ranking of how free that lone pair is. Alkyl groups push electron density toward nitrogen, so simple alkyl amines beat ammonia as bases. A benzene ring does the opposite: it pulls the pair into the ring by resonance, so aromatic amines like aniline are far weaker bases than aliphatic ones.
You can build an amine from a haloalkane plus ammonia, but the product is itself nucleophilic, so it attacks more haloalkane and the pot holds a mixture of primary, secondary, and tertiary amines. Reducing a nitrile is cleaner, turning the triple bond into a CH2NH2 group. To make an amide instead, let an amine attack an acyl chloride: the nitrogen hits the carbonyl carbon, chloride leaves, and HCl is lost overall.
The amide product is not basic, and the reason is the same lone pair. It is now shared with the carbonyl group by resonance, delocalized onto the oxygen, so no free pair remains to take a proton. The C-N bond gains partial double character: flat, rigid, and hard to break. That stubborn link is the peptide bond of proteins and the backbone of nylon and Kevlar.
A free lone pair makes amines basic, and resonance locks it away in amides.
2 · Watch
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Where it sits
8 questions wait behind this lesson, each with its answer explained. Every answer feeds the sky: stars light as they are learned, and dim when it is time to come back.