Amide
The amide has a carbonyl bonded directly to a nitrogen atom — it can be seen as a carboxylic acid where the hydroxyl was swapped for an amino group. It's the bond that forms proteins (peptide bond).
General formula
Amide types
| Type | Structure | Example |
|---|---|---|
| Primary | R–CONH₂ | ethanamide, CH₃CONH₂ |
| Secondary | R–CONH–R′ | N-methylethanamide |
| Tertiary | R–CON(R′)–R″ | N,N-dimethylmethanamide |
Primary, secondary, and tertiary refer to how many carbon groups replace nitrogen hydrogens. They do not describe the carbonyl carbon.
Why is an amide weakly basic?
The nitrogen lone pair delocalizes into the carbonyl. Resonance gives the C–N bond partial double-bond character, makes the group more planar, and makes the lone pair less available to capture H⁺.
Naming rule
Name = main chain (including the carbonyl carbon) + suffix -amide (e.g., ethanamide). Substituents on the nitrogen take the N- prefix.
How to name it with IUPAC
Use this sequence to move from the structure to the systematic name:
- Include the carbonyl carbon in the parent chain.
- Use -amide; substituents on nitrogen receive the N- prefix.
- CH₃CONHCH₃ = N-methylethanamide: ethanamide with methyl on N.
Examples
| Name | Formula |
|---|---|
| Methanamide (formamide) | HCONH₂ |
| Ethanamide (acetamide) | CH₃CONH₂ |
| N-methylethanamide | CH₃CONHCH₃ |
Visual examples
See how the functional group appears inside the chain. Compare the drawings with the formulas in the table to practice visual recognition.
Chemical reading
The nitrogen lone pair delocalizes into the carbonyl, giving C–N partial double-bond character and greatly lowering basicity.
Properties and applications
Protein peptide bonds are amides; nylon, urea, and many medicines also contain this group.
- Hydrolysis breaks C–N. CH₃CONHCH₃ is N-methylethanamide because the substituent is attached to nitrogen.
- Compare polarity, chain size, and hydrogen bonding before predicting physical properties.