Malononitrile
Malononitrile, also propanedinitrile, is a nitrile with the formula CH2(CN)2. Malononitrile is relatively acidic, with a pKa of 11 in water. This allows it to be used in the Knoevenagel condensation, for example in the preparation of CS gas:
In related chemistry, malononitrile is a suitable starting material for the Gewald reaction, where the nitrile condenses with a ketone or aldehyde in the presence of elemental sulfur and a base to produce a 2-aminothiophene.