Three hundred forty-five grams (1.7 moles) of ethyl ethoxalylpropionate, b.p. 114–116°/10 mm. (p. 272), is placed in a round-bottomed flask of suitable size carrying a reflux condenser, and a thermometer is suspended from the top of the condenser into the liquid. The ethyl ethoxalylpropionate is then heated until a vigorous evolution of carbon monoxide begins (130–150°). The temperature of the liquid is gradually raised as the gas evolution diminishes, and finally the liquid is refluxed until no more gas comes off. The ethyl methylmalonate is then distilled. It boils at 194–196°/745 mm., and the yield is 288 g. (97 per cent of the theoretical amount).

Forty-six grams (2 gram atoms) of sodium, cut into small pieces, is added to 1 l. of absolute ethyl alcohol (Note 1) in a 2-l. three-necked flask equipped with a mechanical stirrer and a reflux condenser with a calcium chloride tube. When all the sodium is in solution, 320 g. (2 moles) of ethyl malonate (Note 2) is added. Then 200 g. (2.1 moles) of methyl bromide (Note 3) is bubbled into the stirred solution through a tube (at least 4 mm. in diameter) in the third neck of the flask which dips to the bottom of the solution.

The addition of the methyl bromide consumes about four hours. The reaction proceeds smoothly and with evolution of heat, occasionally reaching the boiling point of the mixture. During the course of the reaction sodium bromide separates. When the addition of methyl bromide is complete, the solution is pale orange and faintly alkaline. It is boiled for an additional half-hour then neutralized with glacial acetic acid and cooled. The sodium bromide is filtered with suction and washed on the funnel with a little cold alcohol. The major part of the alcohol is then removed by distillation at atmospheric pressure (Note 4). The sodium bromide is dissolved in 600–700 cc. of water containing 10 cc. of concentrated hydrochloric acid. The resulting solution (Note 5) is added to the residue from the distillation and the mixture shaken well. The aqueous lower layer is separated from the ester and extracted twice with ether. The ester and ether extracts are combined and dried by shaking quickly with calcium chloride and filtering immediately. The ether is removed, and the ester is shaken for exactly one minute with a cold solution of 10 g. of sodium hydroxide in 30 cc. of water (Note 6). The alkali is drawn off; the ester is washed with dilute acid and dried as before with calcium chloride. It is then distilled in vacuo, and the fraction boiling at 96°/16 mm. is taken. There is almost no fore-run or residue. The yield is 275–290 g. (79–83 per cent of the theoretical amount).