ERROR opening https://cactus.nci.nih.gov/chemical/structure/InChI=1/C4H6O2/c1-3(2)4(5)6/h1H2,2H3,(H,5,6)/f/h5H/file?format=sdf&get3d=True  -- InChI=1/C4H6O2/c1-3(2)4(5)6/h1H2,2H3,(H,5,6)/f/h5H could not be loaded.