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Author: Subject: Frustration with trying to make ammonium formate
thors.lab
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[*] posted on 13-8-2021 at 16:42
Frustration with trying to make ammonium formate


So I've tried three times now to make ammonium formate using ammonium bicarbonate and formic acid. All three times I could only get a tiny fraction of a percent to crystallize out and the rest was a syrupy thing that I assume is mostly formamide.

The procedures for all three runs were simple: add ammonium bicarbonate to flask, add equimolar quantity of formic acid dropwise with stirring until bubbling is done. Then heat to drive off water.

The first run I just heated as hard as I could trying to keep it below the 180ºC that the formamide will decompose at.

The second run I kept it below 130ºC.

The third run I tried to remove all the water at below 110ºC. I thought there was no way at such low temperatures I'd get a signficant amount of formamide production. But still, with TWO MOLES of ammonium bicarbonate I could only get a measily 1.5g of ammonium formate to crystalize out.

What's going on here? What am I doing wrong?

Side note: I might just end up using formamide for my Leuckart rather than struggling again with ammonium formate. If so, what would be a nice way to clean it up? Most things online I can find are more about removing formamide rather than extracting / cleaning it. I can't distill, and I can't find any information about solubility and etc besides that it's miscible with water.




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karlos³
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[*] posted on 13-8-2021 at 16:58


Thats stuff is very deliquescent, it won't crystallise because it is so fucking hygroscopic.

What do you need it for anyways?
CTH hydrogenation?
Because, an aqueous solution would be fine as is already...

But, potassium formiate is even better suited for that purpose, works better as a hydrogen donor(if that is what you're going to use it for, which I'm pretty certain you want to do).
And I think it is neither that horribly hygroscopic either.

If its for the leuckart, formamide is fine, because it will be made in-situ anyways.

If you can't distill, discontinue any chemistry experiments, until you are able to distill again.
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thors.lab
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[*] posted on 13-8-2021 at 17:08


Quote: Originally posted by karlos³  

If you can't distill, discontinue any chemistry experiments, until you are able to distill again.


Silly! I can't distill because formamide decomposes at its boiling point :)

I need the ammonium formate for a Leuckart reaction. Yes, I could use formamide, but according to some paper I'm taking a look at, the formamide + formic acid combo works well but requires me to sequester water and to reflux for 20 hours at much higher temps (175 rather than 125). I'm going to have a hard time keeping my reflux condenser cold for 20 hours. I also don't have a great way to sequester water other than using 3A molecular sieves. Thoughts on whether the sieves will work fine?

I suppose that's the route I'll have to take though if I can't convince this ammonium formate to crystallize. Should I just heat this mixture up to encourage any remaining ammonium formate to dehydrate into formamide?

[Edited on 14-8-2021 by thors.lab]

[Edited on 14-8-2021 by thors.lab]




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karlos³
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[*] posted on 13-8-2021 at 17:52


You can just form the formamide in-situ from aqueous ammonium formiate and then distill the water off over the course of the reaction.
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Fyndium
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[*] posted on 13-8-2021 at 19:50


Perhaps a vacuum distillation in order to remove the water below decomp temp? The stuff won't give up it's water and remain liquid even at sub-zero temps even when boiled up to 150C to extract water without vacuum.

One way would be to bubble ammonia to concentrated formic acid. This forms so much heat that it will cook it off at once unless a large body of coolant bath is used, and eventually it will turn into white porridge that is impossible to stir with other than strong overhead stirring. Probably you can get away with conc. formic acid and ammonium carbonates for the same result. According to SMWiki, it does not dissolve in acetone so rinsing it with that in filter could be used to drive most of the formic acid and water away, leaving mushy cake behind that should be vacuum dried, or used as is. It does not dissolve in ethanol too much neither, though. Residues of formic acid do not matter though, if you are gonna use it in Leuckart. I don't remember now which combo had the best reaction kinetics, but some combinations of formamide/formate/formic acid gave very poor yields, while others were almost quantitative.

You could use dean-stark to extract water during the reaction, or simple distillation and return any reactants back as it comes over. Keeping the condenser cool for 20h should not be an issue, just go get a large enough bucket and replace water if necessary.
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happyfooddance
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[*] posted on 14-8-2021 at 10:24


HCOOH + NH4HCO3 = NH4HCOO + H2O

You are making as many molecules of water as you are of your product.

Use ammonium carbonate, not bicarbonate.
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[*] posted on 14-8-2021 at 14:06


I made some a while ago, I can't remember exactly how the reaction progressed, but it went quite well
I bubbled (wet) ammonia gas into ~50% (IIRC) formic acid, then cautiously evaporated it down, cooled it, and I got some wet slushy crystals that I didn't attempt to dry further

I believe the procedure I followed is here:
https://m.youtube.com/watch?v=CuiLFCaYseo
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karlos³
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[*] posted on 14-8-2021 at 14:41


@thors.lab: you might want to look into this similar reaction instead: http://www.sciencemadness.org/talk/viewthread.php?tid=20153

I always recommend that, when its about leuckart related substrates, and dude, I know you already well enough to understand your usual substrates.
Take a look into this instead, its much less hot, much higher yielding, just maybe a bit more costly thanks to the Ni(II) salts?

I can recommend it though.
I beat the fucking leuckart with substrates that merely give 60% wíth the leuckart.... that fucking Ni-Zn gave me once at least a fucking 84% of primary amine, impossible with the leuckart :cool:

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[*] posted on 16-8-2021 at 01:34


I made some mixing formic acid with anydrous NH3.
If you want to crystallize, you only need to concentrate an ammonium formate water solution under vacuum at 70°C or below.
Then filter and that's it.
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draculic acid69
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[*] posted on 18-8-2021 at 03:37


Try using nh3oh instead of bicarbonate and see if you get a different result
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Fyndium
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[*] posted on 18-8-2021 at 08:19


Mixing formic acid and 35% ammonia does work, and it releases tremendous amount of thick, white smoke as it heats up. Boiling off the water is absolute nightmare, and at 150C the liquid happily just sits there, merely condensing anything, so you really need to hit serious vacuum to it to get rid of most of the water - or then just keep heating to make it into formamide directly, and then vacuum distill it if you like it better. A lot better way is to instead skip the ammonia solution making and directly bubble ammonia into conc formic acid. It will form very thick white sludge soon, and it also forms white cloud, so good ventilation and good stirring (like dough mixer good) is needed, and preferably in a wide mouth vessel or else you have big trouble getting it out from there without using solvents.
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