Dibromomalononitrile-potassium BROMIDE COMPLEX

A. Dibromomalononitrile-potassium bromide complex. In a 2-1. three-necked flask equipped with an efficient stirrer, a dropping funnel, and a thermometer are placed 900 ml. of cold water, 99 g. (1.5 moles) of malononitrile (Note 1), and 75 g. (0.63 mole) of potassium bromide. The flask is then placed in an ice-water bath, the stirrer is started, and the thermometer is adjusted to extend into the liquid but not into the path of the stirrer. When the temperature of the mixture has dropped to 5-10° (much solid crystallizes), 488 g. (158 ml. at 25°, 3.05 moles) of bromine is added over a period of 2.5 hours. The stirring is continued for an additional 2 hours, while the temperature is held at 5-10°. The precipitated solid complex is collected on a Buchner funnel, washed with 150 ml. of ice-cold water and sucked as dry as possible for about 1 hour (Notes 2 and 3). The grainy product is then dried to constant weight in a vacuum desiccator over phosphorus pentoxide, at the pressure obtained with an aspirator (Notes 4 and 5). The yield of light-yellow product is 324 340 g. (85-90%) (Note 3). 

The vapors of dibromomalononitrile-potassium bromide complex are irritating to the eyes and nose. The solid causes discoloration of the skin on contact. Manipulations should be carried out with gloves in a hood. 

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