1-Methyl-2-oxocyclopentanecarbonitrile O-((methylamino)carbonyl)oxime 20417-82-7 BRN 2124666 Cyclopentanecarbonitrile, 1-methyl-2-oxo-, O-(methylcarbamoyl)oxime ENT 27,332 NSC 190932 UC-23619 Union carbide UC-23619