Author Topic: Preparation of Diethylisopropylamine  (Read 1669 times)

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Rhodium

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Preparation of Diethylisopropylamine
« on: August 20, 2003, 12:38:00 PM »
This is a standard non-nucleophilic base, better than triethylamine, and almost as good as diisopropylethylamine (Hünigs base).

Preparation of Diethylisopropylamine
Saul Caspe
J. Am. Chem. Soc. 4457 (1932)

No appreciable reaction takes place between isopropyl bromide and diethylamine on boiling under atmospheric pressure. In early experiments it was found that a yield of 10% was obtained on heating these reactants for forty-two hours in the presence of copper and sodium bromide. The yield was increased to 30% by the use of an autoclave, with the above accelerators, at 140°C for six hours. The reaction was promoted to an even greater extent by the presence of glycerol. A mixture of 123 g of isopropyl bromide, 94.9 g of diethylamine and 50 g of glycerol was gently heated under reflux for 72 h; the resulting amines were liberated with alkali, dried with potassium hydroxide and fractionally distilled, when 67 g (60% of the theoretical amount) of a product boiling at 108° was obtained, A similar yield was obtained when the glycerol was replaced by an equal weight of ethylene glycol; with half that quantity of mannitol, the yield amounted to only 25 g.
Diethylisopropylamine is a colorless liquid, miscible in all proportions with water. Its specific gravity is 0.75.

Vitus_Verdegast

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I think you forgot something
« Reply #1 on: August 20, 2003, 03:45:00 PM »
with half that quantity of mannitol, the yield amounted to only 25 g.


Where is mannitol used here?

Or is it a typo and did you perhaps mean "half the quantity of glycerol" ?


Rhodium

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The author wasn't especially clear...
« Reply #2 on: August 20, 2003, 05:45:00 PM »
No, it is simply bad English.

50g Glycerol -> Yield 60%
50g Ethylene glycol -> Yield ~60%
25g Mannitol -> Yield 25 g

Get it? All the alcohols are essentially CH2OH units, repeated three, two, or six times.

slappy

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Re: This is a standard non-nucleophilic base,...
« Reply #3 on: August 21, 2003, 09:38:00 PM »

This is a standard non-nucleophilic base, better than triethylamine, and almost as good as diisopropylethylamine (Hünigs base).




Don't fool yourself into believing that any of these bases are "non-nucleophilic". There is always some quaternary salt formed., even in systems that you would think would be too sterically hindered. These can be very hard to remove too, often requiring ion-exchange chromatography or something tedious. Sometimes these salts are small (<1%) and sometimes high (2-5%).

Rhodium

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non- is a relative term
« Reply #4 on: August 22, 2003, 01:59:00 AM »
You are correct, instead of the common term "non-nucleophilic" should be replaced with "bases with low nucleophilicity"?