The structure RCONH₂ contains a carbonyl group (C=O) bonded directly to a nitrogen atom (NH₂). This specific functional group, CONH₂, is characteristic of an amide. In the general naming convention for this class of organic compounds, they are known as alkanamides.

Alkylamine: Amines have a general formula of RNH₂ (primary amine) without the carbonyl group (C=O) adjacent to the nitrogen.

Alkanone: Alkanones, also known as ketones, have a carbonyl group (C=O) bonded to two other carbon atoms (RCOR'), and do not contain a nitrogen atom.

Amino acid: Amino acids are organic compounds that contain both an amino group (–NH₂) and a carboxylic acid group (–COOH) attached to the same central carbon atom, along with a hydrogen atom and a variable side chain (R group). The structure RCONH₂ lacks a carboxyl group.

The correct option is C. alkanamide.