Amide

In the usual nomenclature, one adds the term "amide" to the stem of the parent acid's name.

IUPAC recommends ethanamide, but this and related formal names are rarely encountered.

Proteins and important plastics like nylons, aramids, Twaron, and Kevlar are polymers whose units are connected by amide groups (polyamides); these linkages are easily formed, confer structural rigidity, and resist hydrolysis.

Amides include many other important biological compounds, as well as many drugs like paracetamol, penicillin and LSD.

In fact the O, C and N atoms have molecular orbitals occupied by delocalized electrons, forming a conjugated system.

Conversely, under extremely acidic conditions, the carbonyl oxygen can become protonated with a pKa of roughly −1.

Typically amides are less soluble than comparable amines and carboxylic acids since these compounds can both donate and accept hydrogen bonds.

Tertiary amides, with the important exception of N,N-dimethylformamide, exhibit low solubility in water.

[citation needed] Primary and secondary amides do not react usefully with carbon nucleophiles.

When reacted with carbon nucleophiles, N,N-dimethylformamide (DMF) can be used to introduce a formyl group.

[10] Here, phenyllithium 1 attacks the carbonyl group of DMF 2, giving tetrahedral intermediate 3.

Because the dimethylamide anion is a poor leaving group, the intermediate does not collapse and another nucleophilic addition does not occur.

Peptidase enzymes and some synthetic catalysts often operate by attachment of electrophiles to the carbonyl oxygen.

The direct reaction generally requires high temperatures to drive off the water: Esters are far superior substrates relative to carboxylic acids.

[13][14][15] Further "activating" both acid chlorides (Schotten-Baumann reaction) and anhydrides (Lumière–Barbier method) react with amines to give amides: Peptide synthesis use coupling agents such as HATU, HOBt, or PyBOP.