A.
Methyl coumalate. In a
500-ml. round-bottomed flask provided with a
thermometer is placed
139 ml. of concentrated sulfuric acid. To the acid is added, with swirling,
50 g. (0.36 mole) of pulverized coumalic acid (
p. 201) in small portions. The reaction is slightly exothermic, and the mixture is maintained between 20° and 30° by occasional immersion of the flask into an
ice bath.
Methanol (70 ml.) is then added in small portions with frequent swirling, and the temperature is held between 25° and 35°. The mixture is heated on a
steam bath for 1 hour, cooled to about 40°, and poured slowly with stirring into 800 ml. of water in a
2-l. beaker while the temperature is maintained below 40° by an ice bath (Note
1). Anhydrous
sodium carbonate is added in small portions with stirring until the mixture is slightly alkaline (Note
2). The precipitated ester is freed of inorganic salts by slurrying four times with 100-ml. portions of cold water, filtered, and air-dried overnight. The yield of
methyl coumalate, m.p.
68–70°, is
17.5–24.5 g. (
32–45%). This crude product is used for the preparation of
6-hydroxynicotinic acid.