K 138
Ethyl acetoacetate ethylene acetal
A 50-mL round-bottom flask containing a magnetic stirring bar and equipped with a Hickman
still and a reflux condenser was charged with p-toluenesulfonic acid monohydrate catalyst,
(150 mg 0.9 mmol) of ethyl acetoacetate, (2.0 mL, 2.06 g, 16 mmol) of ethylene glycol (1.0
mL, 1.11 g, 18 mmol), and anhydrous toluene (20 mL). The solution was heated under
vigorous reflux for 1 hour. As the reaction progresses, the water formed is separated from the
reaction solution by azeotropic distillation with the toluene. Then, on cooling, the water
separates from the toluene in the upper portion of the Hickman still and collects on the walls
and in the collar while the toluene returns to the distillation flask. As the toluene distillate
collects in the collar of the still, it was removed with a Pasteur pipet.
The flask was cooled to room temperature and the toluene solution extracted with 1 M
aqueous NaOH solution (10 mL) water (2 x 10 mL). The organic solution was dried over
MgSO4 Filtrated and the toluene removed on a rotary evaporator or by distillation. It is
advisable not to heat the liquid residue above 160 °C. This leaves xx g (xx %) of Ethyl
acetoacetate ethylene acetal as a yellow oil. The acetal is sufficiently pure for
characterization. It may be further purified by distillation under reduced pressure.
Mikael Begtrup 26/09/10