Malononitrile is a weak cyanocarbon acid with exceptional reactivity. It is used extensively as a reactant or reaction intermediate since the methylene group and either one or both cyano groups can take part in condensation reactions to give a variety of additional products and heterocyclic compounds. This unique reactivity makes malononitrile an important chemical in research and in medical, industrial, and agricultural chemistry. In the late 1940's malononitrile was used experimentally in the treatment of schizophrenia and depression.