Amides are carboxylic acid derivatives. The hydroxyl group is replaced by ammonia or a primary or secondary amine.
Amides get their degrees based on how many carbon atoms are directly attached to the nitrogen atom. From left to right, the image above shows primary, secondary, and tertiary amides.
Two truths and a lie:
1. the oxygen is sp2-hybridized
2. the carbonyl carbon is sp2-hybridized
3. the nitrogen is sp3-hybridized.
Which one is the lie? The nitrogen is actually NOT sp3. Its electron density is actually distributed with the carbonyl carbon and the oxygen, so it’s actually sp2. Let me prove it to you with a resonance structure:
Pro-tip: whenever an atom can resonate, it will (at least in Orgo 1)! Remember that a molecule with delocalized electron density is more stable, and that more stability means a lower energy state.
What’s the difference? What’s the secret sauce that allows us to distinguish between the two? It's just a carbonyl.
The molecule on the left is an amide, and the molecule on the right is an amine. The amide has an oxygen double-bonded to the carbon directly attached to the nitrogen, but the amine does not. That carbonyl is what makes this nitrogen compound an amide.
Amides are formed in biological systems when amino acids bond to form peptides, which in turn form polypeptides and proteins. They’re also found in local anesthetics like lidocaine.
Hope this quick overview of amides helped! Good luck studying!