An organic compound having molecular mass 60 u is found to contain $\text{C }=\text{ 2}0\%,\text{ H }=\text{ 6}.\text{67}\%\text{ and N }=\text{ 46}.\text{67}\%$ rest being oxygen. On heating, it gives ${\text{NH}}_{\text{3}}$along with solid residue. The solid residue gives violet colour with alkaline copper sulphate solution. The compound is