Org. Synth. 1939, 19, 45
DOI: 10.15227/orgsyn.019.0045
ETHYL HYDROGEN SEBACATE
[Sebacic acid, ethyl acid ester]
Submitted by Sherlock Swann, Jr, René Oehler, and R. J. Buswell.
Checked by Lee Irvin Smith and J. W. Clegg.
1. Procedure
In a 1-l. modified Claisen flask (Note 1), the side arm of which is corked, is placed a mixture of 202 g. (1 mole) of sebacic acid, 150 g. (0.58 mole) of diethyl sebacate (Note 2), 50 cc. of di-n-butyl ether (Note 3), and 30 g. (25 cc.) of concentrated hydrochloric acid (sp. gr. 1.19). A reflux condenser is connected to the top of the distilling flask.
The flask is heated in a Wood's metal bath at 160–170° until the mixture is completely homogeneous. The temperature of the bath is then lowered to 120–130°, and 60 cc. (1 mole) of 95 per cent ethyl alcohol is added to the solution through the condenser. The mixture is allowed to reflux for two hours. At the end of this period an additional 20-cc. portion of ethyl alcohol is poured into the solution and refluxing is continued for two hours longer.
The Wood's metal bath is allowed to cool to about 75° and the reaction mixture is subjected to distillation under reduced pressure, using a water pump (Note 4). The temperature of the bath is increased slowly and distillation is continued, with a water pump, until the bath reaches a temperature of about 125°. The bath is again cooled to 75–80° and the distillation is continued at lower pressure, using an oil pump.
The first fractions consist of a little alcohol, water, and n-butyl ether (Note 5). The next fraction is ethyl sebacate, b.p. 156–158° at 6 mm. (Note 6). Ethyl hydrogen sebacate is collected at 183–187° at 6 mm. The product melts at 34–36° and weighs 114–124 g. (50–54 per cent of the calculated amount, based on the sebacic acid used). Refractionation of the fore-run (b.p. 175–183°/6 mm.) and after-run (b.p. 187–195°/6 mm.) gives an additional 24–26 g. of pure monoester. The total yield is 138–150 g. (60–65 per cent of the theoretical amount) (Note 7) and (Note 8).
2. Notes
1.
The
column of the flask should be at least 35 cm. in length and well insulated. Wrapping the column with 10-mm. asbestos rope is satisfactory.
2.
The addition of diester at the beginning of the reaction decreases its formation from the reactants so that the monoester becomes the main product.
Ethyl sebacate is prepared conveniently by refluxing
130 g. (0.65 mole) of sebacic acid with
250 g. of ethyl alcohol and
25 cc. of concentrated sulfuric acid. The yield is about
90 per cent, and the product boils at
156–158° at 6 mm. See, also,
Note 8, p. 265.
3.
n-Butyl ether is used in preference to other possible compounds because it permits the formation of a homogeneous reaction mixture.
4.
At the beginning of the distillation the liquid in the flask foams excessively. It is advisable, therefore, to reduce the pressure gradually and not to use low pressures until the foaming subsides.
5.
The
n-butyl ether may be recovered in pure condition by a simple distillation after the water has been separated from it.
6.
After the
ethyl sebacate has distilled, it is well to drain the cooling water from the condenser in order to prevent the monoester from solidifying before reaching the
receiver. The recovered
ethyl sebacate weighs
150–175 g. and may be used directly in a subsequent preparation.
7.
In subsequent runs the distillation residue is allowed to remain in the flask. In this way the yield is increased to
70–77 per cent for runs of one and two moles.
8.
The submitters report that
ethyl hydrogen adipate, b.p.
155–157°/7 mm., has been prepared in
71–75 per cent yields on a one-mole scale by the same procedure.
3. Discussion
Ethyl hydrogen sebacate has been prepared by the direct esterification of
sebacic acid with
ethyl alcohol,
1 by the half-saponification of
ethyl sebacate,
2 and by heating equimolecular quantities of
sebacic acid and
diethyl sebacate for several hours.
3
This preparation is referenced from:
Appendix
Chemical Abstracts Nomenclature (Collective Index Number);
(Registry Number)
Sebacic acid, ethyl acid ester
ethyl alcohol (64-17-5)
sulfuric acid (7664-93-9)
hydrochloric acid (7647-01-0)
Ethyl hydrogen adipate (626-86-8)
di-n-butyl ether,
n-butyl ether (142-96-1)
Ethyl sebacate,
Ethyl hydrogen sebacate (693-55-0)
sebacic acid (111-20-6)
diethyl sebacate (110-40-7)
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