In a
1-l. round-bottomed flask fitted with a reflux condenser are placed
192 g. (166 ml., 2 moles) of freshly distilled furfural (Note
1),
208 g. (2 moles) of malonic acid (Note
2), and
96 ml. (1.2 moles) of pyridine (Note
3). The flask is heated on a
boiling water bath for 2 hours, and the reaction mixture is cooled and diluted with 200 ml. of water. The acid is dissolved by the addition of concentrated aqueous
ammonia, the solution is filtered through a
fluted filter paper, and the paper is washed with three 80-ml. portions of water. The combined filtrates are acidified with an excess of
diluted (1:1) hydrochloric acid with stirring. The mixture is cooled by running water and then allowed to stand in an
ice bath for at least 1 hour. The
furylacrylic acid is filtered, washed with four 100-ml portions of water, and dried. The yield of practically colorless needles melting at
141° is
252–254 g. (
91–92%). If a purer product is desired, recrystallization is best effected from dilute alcohol (Note
4). On slow cooling of the solution, needles melting at
141° separate.