1,4-Dioxane, often simply called dioxane because the 1,2 and 1,3 isomers of dioxane are rare, is a heterocyclic organic compound. It is a colorless liquid with a faint sweet odor similar to that of diethyl ether
D 2239 (OTTO) 1,4-Dioxan, for HPLC, 99%+ Cas 123-91-1 - used as an internal standard for nuclear magnetic resonance spectroscopy in deuterium oxide.