In chemistry, an amide is one of three kinds of compounds:

• (sometimes called acid amide) the organic functional group characterized by a carbonyl group (C=O) linked to a nitrogen atom (N), or a compound that contains this functional group (pictured to the right); or
• a particular kind of nitrogen anion.
• any organic compound derived by the replacement of a hydroxyl group by an amino group.

Amides are the most stable of all the carbonyl functional groups.

Many chemists make a pronunciation distinction between the two, saying (IPAEng: əˈmiːd for the carbonyl-nitrogen compound and for the anion. Others substitute one of these pronunciations with /ˈæmɨd/, while still others pronounce both /ˈæmɨd/, making them homonyms.

In the first sense referred to above, an amide is an amine where one of the nitrogen substituents is an acyl group; it is generally represented by the formula: R₁(CO)NR₂R₃ , where either or both R₂ and R₃ may be hydrogen. Specifically, an amide can also be regarded as a derivative of a carboxylic acid in which the hydroxyl group has been replaced by an amine or ammonia.
Compounds in which a hydrogen atom on nitrogen from ammonia or an amine is replaced by a metal cation are also known as amides or azanides.

The second sense of the word amide is the amide anion, which is a deprotonated form of ammonia (NH₃) or an amine. It is generally represented by the formula: 1^-, and is an extremely strong base, due to the extreme weakness of ammonia and its analogues as Brønsted acids.

The remainder of this article is about the carbonyl-nitrogen sense of amide. For examples of the anionic amide, see the articles Sodium amide and Lithium diisopropylamide.

Amide synthesis

• Amides are commonly formed from the reaction of a carboxylic acid with an amine. This is the reaction that forms peptide bonds between amino acids. These amides can participate in hydrogen bonding as hydrogen bond acceptors and donors, but do not ionize in aqueous solution, whereas their parent acids and amines are almost completely ionized in solution at neutral pH. Amide formation plays a role in the synthesis of some condensation polymers, such as nylon and Aramid (Twaron / Kevlar). In biochemistry peptides are synthesized in solid phase peptide synthesis. The Schotten-Baumann reaction describes the formation of amides from amines and acid chlorides.