Oxalic anhydride

Oxalic anhydride or ethanedioic anhydride, also called oxiranedione, is a hypothetical organic compound with the formula C₂O₃, which can be viewed as the anhydride of oxalic acid or the two-fold ketone of ethylene oxide. It is an oxide of carbon (an oxocarbon).

The simple compound apparently has yet to be observed (as of 2009). In 1998, however, P. Strazzolini and others have claimed the synthesis of dioxane tetraketone (C₄O₆), which can be viewed as the cyclic dimer of oxalic anhydride.

It has been conjectured to be a fleeting intermediate in the thermal decomposition of certain oxalates and certain chemoluminescent reactions of oxalyl chloride.