In a
1-l. round-bottomed flask, provided with an efficient and not too narrow
reflux condenser, are placed
25 g. (1.03 gram atoms) of magnesium turnings (Grignard),
25 cc. of absolute alcohol (Note
1),
1 cc. of carbon tetrachloride (Note
2), and
30 cc. of a mixture of 160 g. (151 cc., 1 mole) of ethyl malonate and 80 cc. of absolute alcohol. Provision is made for cooling the flask when necessary in cold water, and the mixture is gently heated until
hydrogen is evolved. The reaction may become so violent that external cooling is necessary. The
ethyl malonate is gradually added through the condenser at such a rate that the reaction proceeds vigorously but not beyond control. When the reaction moderates the flask is cooled and
300 cc. of ether, dried twenty-four hours with
calcium chloride, is added through the condenser. On gentle heating the crystals which have separated are dissolved, and
hydrogen is again evolved for some time without further heating. The reaction is brought to completion on the
steam bath. The flask is then removed from the steam bath, and a mixture of
100 cc. of ethyl chloroformate (1.05 moles) and 100 cc. of dry ether is added through the condenser from a
dropping funnel at such a rate that vigorous boiling is maintained throughout the addition (Note
3). The reaction is complete after heating for fifteen minutes on the steam bath.
The viscous magnesium compound formed is cautiously decomposed with dilute
acetic acid (75 cc. in 300 cc. of water), the flask being cooled under the tap. Two clear layers are formed, and, after separation, the aqueous layer is extracted with
100 cc. of ether, the combined ethereal solution is washed with water and dried with
sodium sulfate, and the
ether is distilled on the steam bath. The residue is distilled under reduced pressure. After a small fore-run the temperature rapidly rises to 130° at 10 mm. when the pure
tricarbethoxymethane begins to distil. The yield of material collected over a five-degree interval is
204–215 g. (
88–93 per cent of the theoretical amount). The product solidifies at 25°. The melting point of the pure substance is
28–29°.