carboxamide

Carboxamide refers to an organic compound containing the amide functional group -CO-NR2, typically derived from a carboxylic acid. The general structure is R-CO-NR'R'' where R, R' and R'' can hydrogen or hydrocarbon groups. Primary amides have the form R-CO-NH2, secondary amides R-CO-NHR', and tertiary amides R-CO-NR'R''. The term encompasses many synthetic and biological amide compounds.

Carboxamides are commonly prepared by coupling carboxylic acids with amines, using coupling reagents such as DCC or EDCI, or by converting the acid to an acyl chloride and then reacting with an amine. They can also form by dehydration of ammonium carboxylates or by reduction of nitriles.

The amide carbonyl and nitrogen are linked by resonance, giving substantial planarity and partial double-bond character to the C-N bond. This reduces the basicity of nitrogen and imparts unique reactivity. Amides are polar and capable of hydrogen bonding, often resulting in high boiling points and variable solubility. N-substitution modulates properties and reactivity.

Hydrolysis of carboxamides yields the corresponding carboxylic acid; they can also be reduced to amines with suitable reagents. Carboxamides find widespread use as solvents (for example DMF, DMAc, NMP) and as building blocks in pharmaceuticals and polymers. The amide linkage is central to biology (peptide bonds) and to synthetic polyamides such as nylons.

Safety: many carboxamides are hazardous or irritants; certain solvents like DMF and DMAc have specific health concerns and should be handled with appropriate precautions.