Amide group

The amide group is originated when a carboxyl group reacts with an amine group. It is characterized by the presence of a carbon bounded to an oxygen through a double bond and to a nitrogen via a single bond.

Indeed, though this is the most common representation, the amide group displays an electronic delocalization involving the oxygen, carbon and nitrogen atoms. That is, the bound between carbon and oxygen is partially double, and the same is valid for the bound between the carbon and the nitrogen. This causes the amide group to present a rigid conformation, where these three atoms define a plane.

The amide group can be located at the end of a molecule, in which case the nitrogen is connected to two hydrogens, or may be in an internal position, causing the nitrogen to be connected to a hydrogen and a second carbon, or two different carbons.

Despite having a nitrogen atom, the amide group does not have a significant alkaline behavior.
In biochemistry the amide group appears in a prominent position because it is the functional group that exists in the peptide bonds.

The amide groups can be identified by infrared spectroscopy (it shows a VCO band at about 1650 cm-1).