Malononitrile
Malononitrile is an organic compound nitrile with the formula. It is a colorless or white solid, although aged samples appear yellow or even brown. It is a widely used building block in organic synthesis.
Preparation and reactions
It can be prepared by dehydration of cyanoacetamide. Most commonly malononitrile is produced by the gas-phase reaction of acetonitrile and cyanogen chloride:About are produced annually. Important outlets include the synthesis of thiamine, the drug triamterene and minoxidil, and the dyes disperse Yellow 90 and disperse Blue 354.
Malononitrile is relatively acidic, with a Acid [dissociation constant|pKa] of 11 in water. This allows it to be used in the Knoevenagel condensation, for example in the preparation of CS gas:
Despite its relative obscurity, Malononitrile is very useful in several reactions, the prime example being a suitable starting reagent 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. It can also be used as a Michael donor.