What is "oxalic anhydride"

n. (context organic compound English) The hypothetical acid anhydride of oxalic acid

Oxalic anhydride or ethanedioic anhydride, also called oxiranedione, is a hypothetical organic compound with the formula CO, 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 (CO), 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.