Org. Synth. 1925, 4, 11
DOI: 10.15227/orgsyn.004.0011
[Malonic acid, butyl-, ethyl ester]
Submitted by Roger Adams and R. M. Kamm.
Checked by F. C. Whitmore and Milton Puterbaugh.
1. Procedure
A 5-l. round-bottomed flask, fitted with a rubber stopper holding a reflux condenser, a separatory funnel, and a mechanical stirrer, is clamped over a steam or water bath. In the flask is placed 2.5 l. of absolute alcohol (Note 1) and then there is added gradually, through the condenser, 115 g. (5 atoms) of clean sodium cut into pieces of suitable size. If the action becomes too violent, the mixture may be cooled by water poured over the outside of the flask. The sodium ethoxide solution is stirred, and cooled to about 50°, after which 825 g. (780 cc., 5.15 moles) of diethyl malonate (Note 2) is added slowly through the separatory funnel. To the clear solution is added gradually 685 g. (535 cc., 5.0 moles) of n-butyl bromide (Note 3). The reaction commences almost immediately and considerable heat is generated. If the addition is too rapid, the reaction may become violent enough to require cooling of the flask by pouring water over it. Up to this point, the time required is about two hours.
The reaction mixture is refluxed until neutral to moist litmus; this requires about two hours. The flask is then connected with a condenser set for distillation. As much alcohol as possible is distilled off by means of the steam or water bath. A period of about six hours is required for this distillation, and about 2 l. of alcohol is recovered.
The residue from which no more alcohol can be distilled is treated with about 2 l. of water and shaken thoroughly. The upper layer of n-butylmalonic ester is separated (Note 4) and distilled under diminished pressure from a 2- or a 3-l. Claisen flask. First a low-boiling portion is collected, consisting of alcohol, water, and butyl bromide; then a small intermediate fraction of unchanged malonic ester comes over; and finally n-butylmalonic ester boiling at 140–145°/40 mm., 130–135°/20 mm., and 235–240°/760 mm. The first fractions amount to less than 100 cc., while the main fraction weighs 860–970 g. (80–90 per cent of the theoretical amount).
2. Notes
1. The quality of the absolute alcohol used has a very marked effect upon the yield. It is desirable to reflux ordinary "absolute" alcohol with about one-twentieth of its weight of sodium and then to distil it directly into the flask in which it is to be used. See Note 2 on p. 249.
A trial run with alcohol of 98.4 per cent purity gave only a 66 per cent yield.
2. The malonic ester used should be redistilled, preferably under diminished pressure, and a 2° fraction used in the preparation. Ordinary commercial malonic ester contains up to 15 per cent of low-boiling impurities.
3. Redistilled n-butyl bromide (p. 28) boiling over a 1° range should be used.
4. It is not practical to filter off the sodium bromide either before or after the distillation of the alcohol, as the separation of the ester from the water layer is then very difficult.
3. Discussion
Ethyl n-butylmalonate can be prepared by the action of n-butyl halides on sodium malonic ester,1 and by the catalytic reduction of a mixture of butyraldehyde, malonic ester, and piperidine in the presence of Raney nickel.2

References and Notes
  1. Bischoff, Ber. 28, 2622 (1895); Adams and Marvel, J. Am. Chem. Soc. 42, 316 (1920); Levene and Taylor, J. Biol. Chem. 54, 351 (1922); Bhide and Sudborough, J. Indian Inst. Sci. A, 8, 89 (1925) [Chem. Zentr. I, 81 (1926)]; Dolique, Ann. chim. 15, 439 (1931).
  2. Wojcik and Adkins, J. Am. Chem. Soc. 56, 2424 (1934).

Chemical Abstracts Nomenclature (Collective Index Number);
(Registry Number)

alcohol (64-17-5)

n-butyl bromide (109-65-9)

sodium bromide (7647-15-6)

Raney nickel (7440-02-0)

sodium (13966-32-0)

piperidine (110-89-4)

sodium ethoxide (141-52-6)

butyraldehyde (123-72-8)

diethyl malonate (105-53-3)

Malonic acid, butyl-, ethyl ester,