1,2-Dihydro-2-oxopyrazine 4-oxide 2(1H)-Pyrazinone, 4-oxide (9CI) 2(1H)Pyrazinone 4-oxide 2-Hydroxypyrazine 4-oxide 3735-46-4 Emimycin Enimycin NSC 119867 Pyrazinol, 4-oxide