In a
300-ml. Claisen flask, whose side neck is elongated by a 10-cm. indented section,
102 g. (1 mole) of acetic anhydride and
0.1 ml. (Note 1) of concentrated sulfuric acid are mixed by hand swirling. The mixture is cooled to 10° by swirling in an
ice bath, then there is added, during about 10 minutes,
96 g. (1 mole) of recently distilled furfural (Note
2). The temperature is maintained at 10–20°. After addition is complete and the contents of the flask have been well mixed by swirling, the
cooling bath is removed and the reaction allowed to warm up spontaneously. A maximum temperature of about 35° is usually reached in about 5 minutes. After the temperature has dropped to that of the room (20–30 minutes),
0.4 g. (Note 1) of anhydrous sodium acetate is added, the flask is fitted for distillation at reduced pressure, and the mixture is distilled from an
oil bath. A fore-run, weighing 50–70 g. and consisting principally of a mixture of
acetic anhydride,
furfural, and
furfural diacetate (Note
3), is collected at 50–140°/20 mm. (Note
4). The product, collected at 140–142°/20 mm., weighs
129–139 g. (
65–70%) and melts at
52–53° (Note
4) and (Note
5).