Organic Syntheses, CV 3, 227
Submitted by W. L. McEwen
Checked by Reynold C. Fuson and E. A. Cleveland.
1. Procedure
A
2-l. three-necked flask, supported in an
oil bath, is fitted with a
mechanical stirrer and an
inlet tube which reaches almost to the bottom of the flask. In it is placed
696 g. (4 moles) of decamethylene glycol, and, after the oil bath is heated to 95–100°, a rapid stream of dry
hydrogen bromide is introduced, with stirring. When the mixture becomes saturated with the gas, as shown by vigorous fuming at the open neck of the flask (Note
1), the temperature of the oil bath is raised to 135° and a slow current of
hydrogen bromide is passed in for 6 hours (Note
2).
After cooling, the crude product is transferred to a
separatory funnel and the lower aqueous layer is drawn off and discarded. The upper layer is washed once with an equal volume of warm water, and then with successive portions of
10% sodium carbonate solution until all acid has been removed. It is then washed once with warm water, which is separated as completely as possible (Note
3). The product thus washed is distilled from a
Claisen flask under reduced pressure. The first few drops of distillate containing some water are discarded: the main fraction distils at
139–142°/2 mm. The yield is
1080 g. (
90%) (Note
4).
2. Notes
1. In larger runs it is advantageous to stop the stirrer and gas stream at this point and allow the lower aqueous layer to separate, after which it is siphoned out.
2. The total quantity of
bromine used is about 950 g.
3. If difficulty is encountered with separation of layers in washing, the substance may be dissolved in an equal volume of
ether.
4. This yield was almost invariably obtained by the submitter, who used quantities of glycol varying from 150 g. to 2 kg.
By the same procedure the following dibromides have been prepared.
3. Discussion
This preparation is referenced from:
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