Org. Synth. 1953, 33, 39
DOI: 10.15227/orgsyn.033.0039
FURFURAL DIACETATE
[2-Furanmethanediol, diacetate]
Submitted by R. T. Bertz
1
Checked by James Cason, William G. Dauben, W. B. Fearing, and B. P. Summerer.
1. Procedure
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).
2. Notes
1.
In order to freeze the equilibrium during distillation, it is imperative that the
sulfuric acid catalyst be previously neutralized by
sodium acetate; hence it is important that the small quantities of
sulfuric acid and
sodium acetate be measured carefully.
2.
The
furfural used by the checkers was collected at 158–163°. In several runs made with technical grade
furfural, which had been stored several years and was black and opaque, a satisfactory product was obtained but yields were
45–53%.3.
This fore-run turns black on standing, but if stored no more than a few days it may be assumed to be an equimolar mixture of
furfural and
acetic anhydride and may be used as starting material for subsequent runs. If no additional runs are to be made, the yield may be increased by 5–10% by redistilling the fore-run.
4.
If collection of the product is started too soon it rapidly darkens and becomes partly liquid on standing. It is advisable to begin collecting the product only after a small sample of distillate, collected separately, sets to a crystalline mass on cooling. Products collected in this manner darkened slightly but remained solid after storage for 2 months. Original distillation of the reaction mixture through a
50-cm. column appeared not to improve the stability to storage, but a sample redistilled in a
Claisen flask remained nearly white after storage for 6 months. All stored samples have a strong odor of
acetic acid.
5.
The submitter has carried out the preparation similarly on a 10-mole scale.
3. Discussion
Furfural diacetate has been prepared from
furfural and
acetic anhydride in the presence of various catalysts, including cation-exchange resins.
2,3,4,5 It has been claimed that the
furfural diacetate preparation of Knoevenagel is improved by the addition of water to the reaction product, followed by ether extraction.
6 The present method is adapted to recovery and reuse of unreacted starting materials.
Appendix
Chemical Abstracts Nomenclature (Collective Index Number);
(Registry Number)
sulfuric acid (7664-93-9)
acetic acid (64-19-7)
acetic anhydride (108-24-7)
sodium acetate (127-09-3)
Furfural (98-01-1)
Furfural diacetate
2-Furanmethanediol, diacetate (613-75-2)
Copyright © 1921-, Organic Syntheses, Inc. All Rights Reserved