= Carboxamide
A \b[carboxamide] is an <amide> of a <carboxylic acid>, with a <carbonyl group> directly bonded to <nitrogen>. Its general connectivity is $\mathrm{R-C(=O)-NR'R''}$, where the substituents shown can include <hydrogen>. The term identifies a class of compounds or a structural unit; <amide bond> identifies the carbonyl C–N bond within it.<IUPAC Compendium of Chemical Terminology, fifth edition (Gold Book)>[C00850, carboxamides, https://doi.org/10.1351/goldbook.C00850 ; A00266, broader amide terminology]{ref}
For example, <acetamide>, $\mathrm{CH_3C(=O)NH_2}$, contains one <carboxamide> group. Replacing an N–H <covalent bond> by an N–C <covalent bond> can leave the defining carbonyl C–N connectivity intact. Conversely, replacing the carbonyl oxygen by another group changes the functional class even though a C–N bond remains. Connectivity, rather than merely an inventory of elements, supplies the classification.
A formal atom balance illustrates <carboxamide> <hydrolysis>:
$$
\mathrm{CH_3CONH_2+H_2O\longrightarrow CH_3COOH+NH_3}.
$$
Both sides contain two carbons, seven hydrogens, one nitrogen and two oxygens. The equation balances neutral molecular formulas; the actual <reaction products> can be protonated or deprotonated according to <pH>. It does not assert that mixing neutral reactants gives rapid conversion. Ordinary amide <hydrolysis> needs suitable conditions or <enzyme> catalysis, consistent with the persistence of <peptide bonds> in water.<Organic Chemistry by John McMurry>[§21.7, Chemistry of Amides: aqueous stability and hydrolysis in acid/base or by biological catalysts]{ref}
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