an 18-carbon saturated fatty acid. The normal numbering system, starting with the carboxylic acid, is shown in blue. The carbons and oxygens of the carboxylic acid functional group are red.

Most organic drugs contain one acid group, usually a carboxylic acid ... in which organic drug molecules A and B are nearly always aromatic: M + A-(e.g., clavulante potassium, phenytoin sodium ...