2-Oxetanone, 4-methylene- 3-Butenoic acid, 3-hydroxy-, .beta.-lactone 4-Methylene-2-oxetanone 674-82-8 Diketene Ethenone, dimer Ketene dimer NSC93783 Vinylaceto-.beta.-lactone WLN: T4VOY DHJ CU1