ETHYLENEUREA2-ImidazolidoneN,N′-Ethyleneurea2-咪唑烷酮2-Oxoimidazolidine环乙烯脲2-Imidazolidone2-imidazolidinonemonoethyleneureaethyleneureaimidazolidin-2-oneimidazolid-2-one2-imidazolidone2-oxomidazolidine2-imidazolidinone2-oxoimidazolidineethylene ureaN,N'-ethyleneurea1,3-ethyleneurea