Org. Synth. 1937, 17, 86
DOI: 10.15227/orgsyn.017.0086
TRICARBETHOXYMETHANE
[Methanetricarboxylic acid, triethyl ester]
Submitted by Hakon Lund and Axel Voigt.
Checked by W. H. Carothers and W. L. McEwen.
1. Procedure
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°.
2. Notes
1.
Anhydrous alcohol is preferable, but a good grade of commercial absolute
alcohol may be used without appreciably lowering the yield. The submitters used alcohol dehydrated by means of
magnesium.
12.
Carbon tetrachloride (as well as a number of other halogen compounds) greatly accelerates the reaction between
magnesium and alcohol. If anhydrous alcohol is used the reaction will start after some time without heating, whereas
99.5 per cent alcohol has to be heated nearly to boiling before the evolution of
hydrogen becomes rapid.
3.
Towards the end of the reaction the
magnesium compound of ethyl methanetricarboxylate separates as a viscous mass which tends to prevent the remaining
magnesium malonic ester and
ethyl chloroformate from reacting. Vigorous boiling keeps the material from forming a compact mass. If larger runs are made it may be necessary to stir during this part of the process.
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3. Discussion
Tricarbethoxymethane has been prepared by the action of
ethyl chloroformate upon
sodiomalonic ester suspended in
benzene,
2 toluene, or
xylene;
3 by the distillation of
ethyl ethoxalylmalonate;
4 from
ethyl carbonate and malonic ester;
5 and by the procedure described above.
6
According to Backer and Lolkelma,
3 the
aromatic esters of methanetricarboxylic acid and the ethyl ester of that acid are best prepared by the Lund procedure using
magnesium; the other
aliphatic esters of methanetricarboxylic acid are best prepared using
sodium—compare the preparation of the trimethyl ester below—with
toluene or
xylene as the reaction medium.
This preparation is referenced from:
Appendix
Chemical Abstracts Nomenclature (Collective Index Number);
(Registry Number)
magnesium compound of ethyl methanetricarboxylate
magnesium malonic ester
ethyl ethoxalylmalonate
aromatic esters of methanetricarboxylic acid
aliphatic esters of methanetricarboxylic acid
alcohol (64-17-5)
calcium chloride (10043-52-4)
acetic acid (64-19-7)
Benzene (71-43-2)
ether (60-29-7)
hydrogen (1333-74-0)
magnesium,
magnesium turnings (7439-95-4)
sodium sulfate (7757-82-6)
carbon tetrachloride (56-23-5)
toluene (108-88-3)
sodium (13966-32-0)
xylene (106-42-3)
ethyl malonate (1071-46-1)
ethyl chloroformate (541-41-3)
ethyl carbonate
Tricarbethoxymethane,
Methanetricarboxylic acid, triethyl ester (6279-86-3)
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