2-Imidazolidone hemihydrate121325-67-5100 % similar Piperazine-2,3-dione13092-86-942 % similar 4-Piperidone hydrochloride hydrate320589-77-335 % similar Arpezine142-63-233 % similar Alloxantin dihydrate6011-27-433 % similar N,N'-Ethylenebisacrylamide2956-58-332 % similar 1,4-Diazepan-5-one34376-54-032 % similar