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Author: Subject: Reductive amination and water
Baphomet
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[*] posted on 3-4-2009 at 18:12


Quote: Originally posted by S.C. Wack  
If anyone has a chemistry book, encyclopedia, or journal that says that the normal ammonium formate or acetate can be crystallized by evaporation from dilute ammonia solutions + acid, I'd love to see it.


I know this is an old thread but this week I had some first hand experience and thought I'd share.

Ammonium Acetate left nothing at all, even upon evaporation out of direct sunlight. It is a phantom above all phantoms ;)

On the other hand it was possible to concentrate a solution of Ammonium Formate over a water bath. Upon cooling, clumps of needle-like crystals appeared spectacularly. This was placed in a dessicator for further drying.

Cheers..




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[*] posted on 13-4-2009 at 19:05


As a follow-up to the last post:

After a week in the dessicator with plenty of CaCl2, the crystals are still not dry.

Should I conclude that this dessicant is not particularly strong, and another should be sought?

Strangely the Amm. Formate crystals 'climbed' up the side of the container, spreading further over time.

If someone knows the best way to dry this, please share it :D




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chemrox
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[*] posted on 13-4-2009 at 21:38


This thread started with a question about water removal during imine formation involving a ketone. I've made them in toluene with a Dean Stark to remove the water and let me know when the reax was complete. A crystal or two of P-toluene sulfonic acid and 48-72 hours were needed. I have to add that I was using anilines and believe that ammonia and Meam may be harder to work with. Then there was a digression regarding the Leukart and the statement was made that formic acid is a watched compound. I wish people would state what country when they say things like that. I'm in the US where formic is not watched. However there's a group that thinks everything here is watched including LAH.



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[*] posted on 14-4-2009 at 01:26


Quote: Originally posted by Baphomet  
As a follow-up to the last post:

After a week in the dessicator with plenty of CaCl2, the crystals are still not dry.

Should I conclude that this dessicant is not particularly strong, and another should be sought?

Strangely the Amm. Formate crystals 'climbed' up the side of the container, spreading further over time.

If someone knows the best way to dry this, please share it :D
Ammonium formate widd dissociate, giving off ammonia that will react with calcium chloride. Maybe replace the CaCl2 with NaOH crystals.
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[*] posted on 14-4-2009 at 18:31


Quote: Originally posted by Mendeleev  
This is very interesting, could you please elaborate on this leuckhard?

Edit: About catalytic hydrogenations, there is a patent, which has dissapeared from the US patent office website which details a catalyst which could potentially bypass the need for fancy and expensive catalysts made with rare metals like platinum, palladium, and rhodium. It is made by reacting copper sulfate pentahydrate with barium or calcium hydroxide to get a catalyst consisting of cupric oxide, and calcium or barium sulfate. The patent is US No. 2,828,343, but like I said, I couldn't find it on the website. I would like to know what kinds of pressures this catalyst requires andhow much of it is needed per mole of imine reduced.

[Edited on 3-12-2004 by Mendeleev]



.....maybe missing but not lost....



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Baphomet
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[*] posted on 25-4-2009 at 01:01


Quote:
Ammonium formate widd dissociate, giving off ammonia that will react with calcium chloride. Maybe replace the CaCl2 with NaOH crystals.


Correcto! The slush smells like formic acid. I had previously considered that such a reaction could take place, and did not think it so, but you are right.

I'll try NaOH.. thanks for the suggestion.

[Edited on 25-4-2009 by Baphomet]




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[*] posted on 9-11-2009 at 15:42


A good compound to remove water from the reaction as it is formed from the reaction (MgSO4 ex.)


wrong mgso4 complexes amines have fun with that expiriment!
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[*] posted on 10-11-2012 at 03:47


Quote: Originally posted by jon  
A good compound to remove water from the reaction as it is formed from the reaction (MgSO4 ex.)

wrong mgso4 complexes amines have fun with that expiriment!


Strangely Merck does not mention this, says MgSO4 is suitable for virtually about everything. I personally also don't think it is so strong acidic that it complexes with amines, but what do I know. But maybe carbonates are better if much slower. Molecular sieves gave ME the impression that they make amines stick to it, but thats subjective.



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[*] posted on 10-11-2012 at 15:40


As mentioned before, much depends on the stability of the imine. In this experiment I obtained 35% yield of 1-dimethylamino-1,2-diphenylethane from the reduction of the enamine of desoxybenzoin and dimethylamine using activated aluminium. The ketone and amine were stirred for 2 hours without removal of water, as the presence of some water is needed for the subsequent reduction. Perhaps more time should be given to allow for the formation of the enamine.



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