Oxamic acid (OA) can be used as a reactant to prepare 6-phenanthridinecarboxamide by direct C-H carbamoylation reaction using ammonium persulfate in DMSO. It can also be used as an organic ligand to prepare functionalized metal oxide nanoparticles for various biological applications. OA along with p-aminobenzoic acid is used to functionalize Au nanoparticles for the development of a sensor to detect Fe3+ ions by the calorimetric method.