Calculations at the CCSD(T)/aug-cc-pVDZ//B3LYP/6-31+G(d) level of theory indicate that singlet neutral OCOCO is unstable with respect to dissociation to CO₂ and CO. In contrast, triplet OCOCO is a stable species provided it can be formed with excess energy of less than 41 kJ mol⁻¹ [the process ³OCOCO → ¹CO + ³CO₂ is endothermic by only 9 kJ mol⁻¹, but the barrier for this process is 41 kJ mol⁻¹]. Triplet OCOCO is not accessible by one-electron oxidation from [OCOCO]−˙ or one-electron reduction from [OCOCO]⁺˙ because neither of these charged species is stable at the level of theory used for these calculations. A report by Cooper and Compton indicates that dissociative electron capture by maleic anhydride results in loss of the elements of C₂H₂ yielding an anion C₂O₃⁻˙. Calculations at the CCSD(T)/aug-cc-pVDZ//B3LYP/6-31+G(d) level of theory suggests that the ion radical C₂O₃⁻˙ may be the stable species [O₂C–CO]⁻˙ provided that the dissociating maleic anhydride radical anion has excess energy of at least 260 kJ mol⁻¹.