Amide ($R-\mathrm{C}(=\mathrm{O})-\mathrm{N}{\mathrm{R}}^{\prime }{\mathrm{R}}^{\prime \prime }$)

Here an amide means a carbonyl group whose carbon is bonded directly to nitrogen; each of $R$, $R^{\prime }$ and $R^{\prime \prime }$ may be hydrogen or a group attached through carbon. A peptide bond contains this linkage. Chemical resonance distinguishes its nitrogen from that of an amine. ^[ref] and ^[ref]

An N-methoxy-N-methyl amide that can form a chelated tetrahedral intermediate on organometallic addition. Controlled hydrolysis gives a ketone rather than immediate repeated addition.

An N-acyl-substituted enamine. Metalated enamines are also called enamides in organometallic usage; a lithiated enamide denotes that distinct anionic form.

Interconversion of amide rotamers requiring loss of favourable nitrogen–carbonyl overlap near a twisted transition region. Solvation can change the barrier relative to the starting planar amide.

Delocalization of a nitrogen lone pair into a carbonyl group, represented by neutral and charge-separated resonance contributions. It gives the C–N linkage partial double-bond character.

A cyclic amide. Its nitrogen–carbonyl connectivity distinguishes it from an ordinary cyclic ketone.

Nα-benzoyl-DL-arginine-p-nitroanilide, a synthetic substrate releasing p-Nitroaniline in the trypsin colorimetric assay.^[ref]