In a
2-l. three-necked round-bottomed flask, equipped with a
reflux condenser attached to a
gas trap, a
dropping funnel, and a
mechanical stirrer, are placed
100 g. (0.9 mole) of furoic acid (Note
1) and 440 ml. of water. The flask is immersed in a pan of crushed ice, and
686 g. (220 ml., 4.3 moles) of bromine is placed in the dropping funnel. The stirrer is started, and the
bromine is added over a period of about 1 hour with constant stirring and cooling (Note
2). The
bromine is decolorized almost immediately at first and then more slowly as the reaction proceeds. The mixture is then heated to boiling and refluxed for 30 minutes. The condenser is removed and the boiling continued for an additional 30 minutes with one neck of the flask open. The mixture is cooled and chilled thoroughly, whereupon the
mucobromic acid separates and is collected on a filter. The filter cake is removed and thoroughly triturated with a solution of
5 g. of sodium bisulfite in 150 ml. of water (Note
3), and the product is again removed by filtration. After drying in the air the crude product weighs
155–170 g. (
67–73%) and melts at
120–122° (cor.).
The
mucobromic acid may be recrystallized by solution in 250 ml. of boiling water with the addition of
2 g. of Darco. The hot solution is filtered, and the filtrate is thoroughly chilled in an
ice bath. After filtration and drying there is obtained
148–155 g. (
64–67%) of white crystals melting at
123–124° (cor.).