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Ninja
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shocked.gif posted on 22-9-2009 at 09:37
Ammonium acetate


Hello!

I tried to synthesize ammonium acetate via 25% acetic acid and ammonium carbonate.
It most likely worked only by putting these reagents in a pot, after the CO2 production ceased. Using a slight excess of ammonium carbonate i heated this mix about half an hour at 75C. The volume was reduced by 30% when finished.
But i was not able to precipitate the product... even at about -10C. :(
I tried adding ethanol (soluble at 10g/l) and acetone (less soluble?).
Cooking the water away is not a good solution, because ammonium acetate is instable at elevated temperatues (>90C). Acetamide would be formed. Hydrolysis products like acetic acid and ammonia are more volatile and wouldn't form a major impurity in the product.

I don't want to use (pure) acetic acid because it's significantly higher cost.

Do you have any suggestions?
Thanks!
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Ozonelabs
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[*] posted on 22-9-2009 at 09:49


Other than buying it (relasitically, the cheaper option)- you probably will have to use GAA. This is due to the incredible water solubility (148 g/100 ml (4 °C)). Even adding EtOH wont help due to incredible solubility in low alkan-ol's ( MeOH 7.89 g/100 mL (15 °C)).

(Solubility quantities from Wikipedia)




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Ninja
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[*] posted on 22-9-2009 at 10:09


Quote: Originally posted by Ozonelabs  
Other than buying it (relasitically, the cheaper option)- you probably will have to use GAA. This is due to the incredible water solubility (148 g/100 ml (4 °C)). Even adding EtOH wont help due to incredible solubility in low alkan-ol's ( MeOH 7.89 g/100 mL (15 °C)).

(Solubility quantities from Wikipedia)

Buying is not an option.
Ethanol is more suitable for precipitation (~1g/100mL) but it doesn't work...
What was my mistake? I used quite pure reagents and tried it multiple times.
Bubbling anhydrous ammonia through pure acetic acid is too much effort and way too expensive (drying ammonia etc.).
Maybe i try to concentrate my AA by boiling a little and continue as above.
Does anyone know the solubility of ammonium acetate in acetone? I just found out it is "slightly soluble" in comparison to "soluble" in ethanol.
Can this mix (water(/acetone?)/ammonium acetate) be dried with something cheap?

Or can ammonium acetate be made of acetamide? I guess it would require rather high pressures or very much time...

[Edited on 22-9-2009 by Ninja]

[Edited on 22-9-2009 by Ninja]
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[*] posted on 22-9-2009 at 10:44


I think it is best to use acetic acid in excess of the carbonate (because it can evaporate) - then you have only the wanted salt in water, and not any contamination.

Maybe try slow evaporation in a warm oven, if you do not want to heat strongly. Then crystallize the remaining salt, if it is not pure as you want.

I have not done this - but it sounds ok to me!


Maybe it is better to use ammonia rather than carbonate? Then there is no chance of carbonate residue in the end product.

[Edited on 22-9-2009 by sonogashira]
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Ninja
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[*] posted on 22-9-2009 at 11:48


Quote: Originally posted by sonogashira  

Maybe it is better to use ammonia rather than carbonate? Then there is no chance of carbonate residue in the end product.

Ammonia has to be dried and requires much a more complex apparatus, to prevent smelling.
I heated this ammonium carbonate some time to 75C mix to decompose it (occurs at >58C), until no ammonia was detectable. By doing this, impurities in my product are greatly reduced.
My mistake was probably to think that i used pure reagents. I used "Hirschhornsalz" a nowadays really uncommon leavening agent in germany. But i just found (RÖMPP) out that mixtures of one part ammonium carbonate, two parts ammonium bicarbonate and little amounts of ammonium carbamate ("1 Teil (NH4)2CO3 und 2 Teilen (NH4)HCO3 mit kleinen Mengen Ammoniumcarbamat") are sold today under the same name. It is said to decompose at (about) the same temperature to the same products (NH3/CO2/H2O) with an obviously different ratio between them.

Precipition did not work because of residual amounts of acetic acid, which increased the solubility of ammonium acetate.
I'm just trying to redo the synthesis with a very big excess of "Hirschhornsalz".
Thanks for the help!
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entropy51
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[*] posted on 22-9-2009 at 12:21


Roscoe's Treatise on Chemistry (in Forum Library) says the crystals can be had by either:

(a) evaporate the solution in a current of NH3, or
(b) glacial acetic is saturated with NH3 gas, or
(c) hot glacial is saturated with (NH3)2CO3 and then cooled

I suspect that dilute acetic will only give crystals using method (a) because otherwise NH3 is lost from the acetate, as stated in Roscoe.
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[*] posted on 22-9-2009 at 12:33


(Reply to the message above mr entropy :) )
When ammonia (in water) is mixed with dilute acetic acid it will give ammonium acetate only (dissolved in water). All that is needed for a pure product is to then evaporate the water. It will not smell when the ammonia is neutralized with acetic acid.

I think you are making it too complicated. An excess of ammonium carbonate will be hard to remove afterwards - best to use slight excess of acetic acid , which can then be evaporated and will not contaminate the product.

But I would recommend to try and remove all the water with slow evaporation, then purify the powder that remains (If it needs - likely it does not.)

[Edited on 22-9-2009 by sonogashira]
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[*] posted on 22-9-2009 at 13:08


Dr. Entropy is not an expert on chemistry.

But Sir Henry Roscoe was definitely an expert.

Sir Henry says ammonium acetate loses NH3, thus leaving acetic acid behind.

Dr. Entropy thinks that is why Ninja is getting no solid product.:P
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[*] posted on 22-9-2009 at 13:22


Hehe, it was meant to be "this is a reply.." - but it ended as a challenge!
I would still think gentle evaporation is ok...
But Sir Henry is the man to trust in these situations!
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[*] posted on 22-9-2009 at 21:06


Ammonium acetate solution indeed does lose ammonia on heating, even solutions of ammonium sulphate lose some ammonia when heated near boiling.

The NH3 gas used does not have to be really dry, even that boiled off from strong aqueous ammonia is usable. I'd evaporate the solution in a slow stream of ammonia, mixing ammonium sulphate with Ca(OH)2 and a little water is a decent way of generating it.

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[*] posted on 23-9-2009 at 04:45


It is true, ammonium acetate can not be isolated from aqueous solutions just by simple evaporation. This was already discussed in the old thread dedicated to ammonium acetate (I suggest to the original poster to search if the topic was already discussed before opening a new thread). As far as I remember, there are several different forms of ammonium acetate because the NH3:CH3COOH ratio in the crystalline salt is not exactly 1:1.

Ammonium carbonate is not exactly what it might sound from its formal name. If you check the pKa's of its ions you can note that ammonium carbonate as such can not exist. It would be more appropriate to call it ammonium carbamate. Indeed, its aqueous solutions are equilibria composed of CO2, NH3, NH4(+), H2NCOO(-), HCO3(-) and CO3(2-).




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[*] posted on 3-10-2009 at 17:51


Quote: Originally posted by Ninja  
Hello!

I tried to synthesize ammonium acetate via 25% acetic acid and ammonium carbonate.
It most likely worked only by putting these reagents in a pot, after the CO2 production ceased. Using a slight excess of ammonium carbonate i heated this mix about half an hour at 75C. The volume was reduced by 30% when finished.
But i was not able to precipitate the product... even at about -10C!


That won't work. NH4-acetate is a salt of a weak acid and a weak base. Try boiling off the water, and all you'll do is boil off the ammonia as well.

Here's how I prepared NH4-acetate:

Poured glacial acetic acid to a depth of about 1.5" in a 250mL beaker. Then I half-way filled a 500mL flask with concentrated NH4OH, with a stopper fitted with two glass tubes, one running to the bottom of the flask, and another that just cleared the stopper. The long glass tube was connected to a small aquarium air pump. Connected a rubbber hose with another glass tube to the short tube.

Start the air pump, and dip the glass tube into the GAA. At first, this produces very heavy, white fumes that leave an oily trace on whatever it touches, so definitely do this under a fume hood. After a few seconds, that stops, and the air simply bubbles through the GAA. There will be no trace of an ammonia odor.

After a few minutes, solid material will begin to appear. At this point, it is essential to use the glass tube as a stirring rod and keep everything in constant motion. Eventually, this becomes quite difficult, but do your best as the solids precipitate. Eventually, the whole mass turns solid, but keep the gas flowing until a strong ammonia odor reappears. Then you're done.

Carefully score the solid mass with a knife if you don't want the beaker to break. Score at right angles (i.e. '+') until you cut all the way through. Pry out one quarter section, and the rest will follow easily. Crush and pulverize the solid mass, and spread on a large watch glass in a thin layer. Dry under a heat lamp (100W, four feet above the watch glass). You'll notice wisps of unreacted acetic acid. After an hour or so, you'll notice nice, long needle-like crystals forming.

You can then turn the material over (like turning a compost pile) and drying the portion that was on the bottom. Again, you'll see those crystals forming. After drying for several hours, you can store it in air tight bottles. It'll keep for months. It's essential to keep it away from atmospheric moisture, since NH4-acetate absorbs moisture, and that will eventually ruin it.

I didn't bother with getting rid of any residual acetic acid since this NH4-acetate was going to be used for Walther-Knoevenagle condensations in acetic acid anyway, so what was the point? It worked just great for that.

If you need to get rid of the unreacted acetic acid, you're on your own.
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[*] posted on 6-10-2009 at 06:05


Some ideas to remove the water in order to get solid NH4OAc:

1. Azeotropic water removal with the aid of a low boiling solvent like DCM ---> no decomposition by heat, cause temperature is in the range of approx. 40°C
2. Remove the water in vacuum at low temperatures. I believe that this is possible and the solution doesn´t split off NH3.
3. Get a solution as concentrated as possible (possible without decomposition) and add a solvent which is miscible with water but in which NH4OAc is not appreciably soluble. Yes I know ethanol was tried. But why not try isopropanol or even THF? You can recover the solvent if you think THF (for example) is too expensive for this application.
4. Crazy idea: put the solution on a mild heating source (I guess 50°C are ok) and blow off the water with a powerful airflow. Then seed the solution (if you have a crystal of NH4OAc) and cool down. Filter off the crystallized product and repeat the procedure with the remaining solution originating from the filtration process. I don´t know if it works but I think it´s worth a trial.
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[*] posted on 6-10-2009 at 23:07


Try acetone. It works well to precipate other acetates (tried on Ca, Pb, Ba, Na) which are generally a PITA to get them to crystallize.

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[*] posted on 30-12-2009 at 18:34


You need to dry your ammonium acetate under a vacuum, keeping the temperature below 60 ° C to avoid decomposition :cool:



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[*] posted on 30-12-2009 at 23:54
ammonium acetate synthesis


Hello everyone! I have been lurking here for over two years, so I figured its about time I join and contribute something to the forum.

Anyway I recently prepared 12.21 grams of fairly pure ammonium acetate. I made the compound by bubbling ammonia gas through 12ml of glacial acetic acid. This took about 45 for the reaction to finish, and once it was done I was left with 12.21 grams of damp ammonium acetate crystals. The crystals smelled like acetic acid, but could very easily be dried with a little more ammonia.

Overall this was a very easy synthesis to preform and the yield is pretty good. Also Ninja, I know you said you did not want to use GAA because it is more expensive, but I think you really should consider buying some its quite cheap and is a useful chemical to have.
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[*] posted on 1-1-2010 at 20:05


It's even easier to react ammonium carbonate with glacial acetic acid to obtain ammonium acetate :cool:



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[*] posted on 20-1-2010 at 17:20


Well ammonium carbonate and acetic acid may be simpler, but it would less pure ( I think). The reason being that your going to have to use an excess of one of the two chemicals, neither of which are very easy to get rid of.

Now using ammonia gas and acetic acid is very simple, and you end up with a fairly pure product. I just did the reaction again have a look!



acetic acid solution.jpg - 28kB
This is a 250ml flask that is holding 30ml of GAA, and that long glass tube is a 24/40 long stem gas adapter (i think that is what its called)



ammonia generator.jpg - 33kB
This next picture is a 500ml fbf holding 60 grams of fertilizer grade urea, and that hose is going to the glassware in pic1



final product.jpg - 20kB
And this is the finished product after two different runs. I do not remember what the final weight was, but I think it was close to 33 grams.
Anyway this in my opinion is much easyer and more efficient way of producing pure ammonium acetate from easy to obtain chemicals. Hope you all enjoy the pictures!
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[*] posted on 21-1-2010 at 15:20


Have to agree with Foss_Jeane and mnick12, tried different methods and only that way was satisfactory.

Made about a kilo of the stuff that way, only left the ammonia gas streaming into the solid ammonium acetate for a couple hours to really saturate it and convert all the GAA. Feel I need to mention that I dried my NH3 gas, since I just boiled it out of 25% NH3.

tried everything grind suggested, did not work, only used up ALOT of my time and wasted even more chemicals.




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[*] posted on 18-11-2012 at 07:23


ok i tried to synthesize amonnium acetate.
I mixed %25 10gr Nh3 with %20 74 gr acetic acid.
i mixed-shaked it in flask 10 mins.
Then i evaporated the water with heating it. At this point i know that i could be turn in to acetamide but it doenst matter. Acetamide is what i really want. But the problem is after i evaporate the water there wasnt anything in flask. Only a white spot at base. It should be much much more .

Everyone saying that they get their product by mixinh NH3 and acetic acid solution.

But when i do nothing is formng. I think they donr react or should wait 1 day before evaporate the water. When i distillling it i smell acetic acid . That should be a proof to they dont react. What could be the problemi
/ why they dont react ??

[Edited on 18-11-2012 by Myeou]
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[*] posted on 19-11-2012 at 08:25


Quote: Originally posted by Myeou  
ok i tried to synthesize amonnium acetate.
I mixed %25 10gr Nh3 with %20 74 gr acetic acid.
i mixed-shaked it in flask 10 mins.
Then i evaporated the water with heating it. At this point i know that i could be turn in to acetamide but it doenst matter. Acetamide is what i really want. But the problem is after i evaporate the water there wasnt anything in flask. Only a white spot at base. It should be much much more .

Everyone saying that they get their product by mixinh NH3 and acetic acid solution.

But when i do nothing is formng. I think they donr react or should wait 1 day before evaporate the water. When i distillling it i smell acetic acid . That should be a proof to they dont react. What could be the problemi
/ why they dont react ??

[Edited on 18-11-2012 by Myeou]


acetamide, acetic acid, ammonia and water evaporated at high temperatures

so nothin remains
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