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All 5 posts Subject: Preparation of Diethylisopropylamine Please login to post Down

Rhodium
(Chief Bee)
08-20-03 19:38
No 454731
User Picture       Preparation of Diethylisopropylamine
(Rated as: good read)

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
(Hive Bee)
08-20-03 22:45
No 454754
User Picture       I think you forgot something

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" ?

A Dream Within A Dream (http://www.poedecoder.com/Qrisse/works/dreamw.html)

Rhodium
(Chief Bee)
08-21-03 00:45
No 454763
User Picture       The author wasn't especially clear...

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
(Hive Addict)
08-22-03 04:38
No 454963
      Re: This is a standard non-nucleophilic base,...

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
(Chief Bee)
08-22-03 08:59
No 454996
User Picture       non- is a relative term

You are correct, instead of the common term "non-nucleophilic" should be replaced with "bases with low nucleophilicity"?

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	All 5 posts		Subject: Preparation of Diethylisopropylamine		Please login to post		Down


		Rhodium (Chief Bee) 08-20-03 19:38 No 454731				Preparation of Diethylisopropylamine (Rated as: good read)
						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 (Hive Bee) 08-20-03 22:45 No 454754				I think you forgot something
						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" ? A Dream Within A Dream (http://www.poedecoder.com/Qrisse/works/dreamw.html)



		Rhodium (Chief Bee) 08-21-03 00:45 No 454763				The author wasn't especially clear...
						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 (Hive Addict) 08-22-03 04:38 No 454963				Re: This is a standard non-nucleophilic base,...
						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 (Chief Bee) 08-22-03 08:59 No 454996				non- is a relative term
						You are correct, instead of the common term "non-nucleophilic" should be replaced with "bases with low nucleophilicity"?

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