2,4(1H,3H)-Pyrimidinedione 2,4-Dihydroxypyrimidine 2,4-Dioxopyrimidine 2,4-Pyrimidinediol 2,4-Pyrimidinedione 66-22-8 Hybar X NSC3970 Pirod Pyrod RU 12709 URACIL Ura