Potassium hydrogenacetylenedicarboxylate is a potassium salt with chemical formula KC4HO4 or K+·HC4O4−, often abbreviated as KHadc. It is often called potassium hydrogen acetylenedicarboxylate or monopotassium acetylenedicarboxylate.
The salt can be obtained from acetylenedicarboxylic acid and is a common laboratory starting material for the synthesis of other derivatives of that acid. In the crystalline form, the hydrogenacetylenedicarboxylate anions HC4O4−s are joined into linear chains by uncommonly short hydrogen bonds. [1][2]