Ethylene dione or ethylenedione, also called dicarbon dioxide, Carbon peroxide, ethenedione, or ethene-1,2-dione, is a chemical compound with the formula C2O2 or O=C=C=O.

[3] In 2015, a research group reported the creation of ethylenedione — by using laser light to eject an electron from the corresponding stable singly-charged anion C2O−2 — and its spectroscopic characterization.

[4] However, the reported spectrum was later found to match that of the oxyallyl diradical, (H2C•)2CO, formed by rearrangement or disproportionation under the high-energy experimental conditions rather than simple electron loss.

[7][8] Recent theoretical computations suggest that the in situ preparation and characterization of ethylenedione may be possible through low-energy free-electron induced single-molecule engineering.

[1] In the 1940s, Detroit physician William Frederick Koch claimed that he had synthesized this compound, which he called glyoxylide, and that it was an antidote to the toxins that caused a long list of ailments, including diabetes and cancer.