The removal of two protons yields the acetylenedicarboxylate dianion C4O2−4, which consists only of carbon and oxygen, making it an oxocarbon anion.

[2][3][4] It can be obtained by treating α,β-dibromosuccinic acid with potassium hydroxide KOH in methanol or ethanol.

Fatty alcohol esters of acetylenedicarboxylic acid can be used for the preparation of phase change materials (PCM).

Salts of this anion are of interest in crystallography because they contain unusually short and strong hydrogen bonds.

In many crystalline salts (with the exception of the lithium one), the HADC units form linear chains connected by strong hydrogen bonds.