Org. Synth. 1938, 18, 13
DOI: 10.15227/orgsyn.018.0013
β-BROMOETHYLAMINE HYDROBROMIDE
[Ethylamine, 2-bromo-, hydrobromide]
Submitted by Frank Cortese
Checked by C. S. Marvel and C. L. Fleming.
1. Procedure
One kilogram (16.4 moles) of ice-cold ethanolamine (Note 1) is added, through a dropping funnel, with mechanical stirring, to 7 l. (9.94 kg., 52 moles) of ice-cold hydrobromic acid (sp. gr. 1.42) (Note 2) contained in a 12-l. round-bottomed flask. The flask is attached to an efficient fractionating column and heated until 1850 cc. of distillate has been collected. The rate of heating is then diminished to a point at which the liquid ceases to distil and merely refluxes. The heating under reflux is continued for one hour. At the end of this time, 700 cc. more is distilled, and the solution is again heated under reflux for one hour. This procedure is followed with 600-, 300-, 250-, 150-, 100-, and 50-cc. portions of distillate. The process may be interrupted at any time. The solution is finally heated under reflux for three hours, and 2.3 l. of crude hydrobromic acid distilled. The total volume of distillate, including that which is collected during refluxing, must not be less than 6270 cc. or more than 6330 cc.
The dark-colored residue is divided into two approximately equal portions, and each is poured, while still hot, into a 4-l. beaker. After the liquid has cooled to about 70°, 1650 cc. of acetone is added to each portion. The mixture is stirred well, so that as much as possible of the dark-colored solid is brought into contact with the acetone. After standing in the icebox overnight, the β-bromoethylamine hydrobromide is collected on a filter, washed with acetone until colorless (Note 3), and air-dried for about fifteen minutes. The filtrates are combined, concentrated to a volume of 1 l., and cooled. After seeding, a second crop of nearly pure material is obtained. By evaporation to a syrup, cooling, and seeding, a third crop of slightly colored material is obtained. (Note 4). The yield is about 2.8 kg. (83 per cent of the theoretical amount) (Note 5).
2. Notes
1.
Commercial
ethanolamine is fractionated in a glass apparatus, and the fraction boiling at
167–169° is used.
2.
The
hydrobromic acid must have a specific gravity of at least 1.42.
3.
It may be advisable for effective washing to transfer the crude cake to a
mortar and crush it.
4.
All three crops are suitable for use in the synthesis of
taurine described on
p. 564.
5.
The procedure has been applied to the preparation of the following β-dialkylaminoethyl
bromide hydrobromides.
|
|
BrCH2CH2NHR2Br
|
|
R
|
Yield, Per Cent
|
Heating Periods
|
|
| CH3 |
83 |
1–1.5 hr., 2 hr. |
| C2H5 |
80 |
1 hr., 2 hr. |
| n-C3H7 |
55 |
0.75 hr., 2 hr. |
| n-C4H9 |
20 |
1 hr., 3 hr. |
| n-C4H9 |
59 |
0.5 hr., 2 hr. |
|
The final distillation was not always carried as far as called for by the procedure of Cortese. If a faint brown or violet color appeared in the distillate, or if white fumes were given off, the distillation was discontinued; further distillation seemed to cause decomposition. However, the color always came near the end point specified in the procedure above and the total volume of the distillates was never less than 95 per cent of that called for. Since the solubilities of the products in acetone range from very slight to extreme as the molecular weights increase, the extraction of the products requires variations in the amounts of acetone specified above. [Lawrence H. Amundsen and Karl W. Krantz, private communication, and J. Am. Chem. Soc. 63, 305 (1941).]
3. Discussion
β-Bromoethylamine hydrobromide has been prepared by the reaction of
potassium phthalimide with
ethylene bromide, followed by hydrolysis;
1 by the addition of
hydrogen bromide to
ethyleneimine;
2 from
ethanolamine and
hydrobromic acid;
3 and from
ethanolamine and
hydrogen bromide at 140–190°.
4 The preparation from
ethyleneimine and
hydrogen bromide is reported to succeed only if the imine is added to the acid.
5
This preparation is referenced from:
Appendix
Chemical Abstracts Nomenclature (Collective Index Number);
(Registry Number)
bromide (24959-67-9)
HYDROBROMIC ACID,
hydrogen bromide (10035-10-6)
acetone (67-64-1)
Potassium Phthalimide (1074-82-4)
ethylene bromide (106-93-4)
β-Bromoethylamine hydrobromide,
Ethylamine, 2-bromo-, hydrobromide (2576-47-8)
ethanolamine (141-43-5)
Taurine (107-35-7)
ethyleneimine (9002-98-6)
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