1. Structure
- Amines → Contain a nitrogen atom bonded to hydrogen and/or alkyl/aryl groups. (General formula: R–NH₂, R₂NH, R₃N).
- Amides → Contain a nitrogen atom directly bonded to a carbonyl group (C=O). (General formula: R–CONH₂, R–CONHR, R–CONR₂).
2. Functional Group
- Amine → Has an amino group (–NH₂).
- Amide → Has a carbonyl group attached to nitrogen (–CONH₂).
3. Polarity
- Amines → Moderately polar, because nitrogen is electronegative but there is no carbonyl group.
- Amides → Highly polar, due to the strong dipole of the carbonyl (C=O) and resonance between C=O and C–N bonds.
4. Hydrogen Bonding
- Amines → Can form hydrogen bonds, but weaker than amides.
- Amides → Strong hydrogen bonding (especially primary and secondary) due to both C=O and –NH groups.
5. Melting and Boiling Points
- Amines → Lower boiling points than amides of similar size.
- Amides → Much higher melting and boiling points, because of strong hydrogen bonding and resonance stabilization.
6. Solubility in Water
- Amines → Usually soluble, especially lower amines, due to hydrogen bonding with water.
- Amides → Even more soluble when small, because they can both donate (via –NH) and accept (via C=O) hydrogen bonds. Solubility decreases as chain length increases.
7. Basicity
- Amines → Stronger bases, because the lone pair on nitrogen is free to accept protons.
- Amides → Much weaker bases, because the lone pair on nitrogen is delocalized (shared with the carbonyl group through resonance), so it is not easily available for protonation.
8. Chemical Reactivity
- Amines → React easily with acids (form salts), with alkyl halides (form substituted amines), and can act as nucleophiles.
- Amides → Generally less reactive, but can undergo hydrolysis (to form carboxylic acids and amines) under strong acidic or basic conditions.
In short:
- Amines = contain –NH₂, are more basic, less polar, lower boiling points.
- Amides = contain –CONH₂, are less basic, more polar, higher boiling points, stabilized by resonance.