Sciencemadness Discussion Board - Guanidine HCl to Guanidine Acetate

Guanidine HCl to Guanidine Acetate

Organikum - 16-9-2022 at 07:40

So I want to turn Guanidine.HCl into Guanidine Acetate for the usual nefarious purposes.

I tried Sodium Methoxide in Methanol and endet up with a flask full of milk, at least it looks like milk and nothing settles. My mistake, I should have used Ethanol or IPA, I underestimated the solubility of NaCl in MeOH which causes the problem.
Added some Ether and in the freezer and I hope I will be able later to do some filtration.

Meanwhile I did some more reading up and it appears that Guanidne Base is kinda allergic against acids except very weak ones. It was suggested to dilute the GAA to 0,1 N what would lead to pretty large volumes of solvent.

I will try with a higher concentration but as cold as possible (about - 20°C for me) and hope I don't trigger to much side reactions.

That's the situation now, but for the next time I want to do this different, I found out that Silver acetate or Thallium acetate in EtOH will do the job and this would be the best method. I agree, just a small problem, my russian silver mines are at the moment unaccessible and I spent all my Thallium on resolving some problems with obnoxious relatives (with good success btw.).

Any suggestions what other more common metal-acetates could be used? Why Silver and Thallium? All I fathom it is about solubility.
Would Sodium or Potassium Acetate in Ethanol or IPA not suffice, the almsot insoluble NaCl dropping out driving the methatesis to completion?

thx
/ORG

unionised - 16-9-2022 at 08:04

Lead acetate solution would be the "classic" option, but a bit toxic.
As you surmised, it's about (aqueous) solubility. Lead acetate is soluble, lead chloride isn't.

An ion exchange resin column loaded with hydroxide would convert the guanidinium chloride to hydroxide which you could then titrate against acetic acid.

Organikum - 17-9-2022 at 07:15

Lead? Still better then Thallium. Darn, I should have bought the big lump of lead on offer lately for cheap on Ebay-KAZ.

I am actually trying to keep this anhydrous for the followup reaction doesn't like water, also water introduces another plethora of possible but undesired side-reactions. Those nitrogen compounds, guanidines and cyanamides seem all to be quite the snowflakes

Thanks.
Gotta dig up some reasonable pure lead for next time and now see what I can save from the mess.
/ORG

Addon:

Quote:

An ion exchange resin column loaded with hydroxide

You mean if I activate a new Britta waterfilter cartouche with NaOH solution it will turn guanidine.HCl into guanidine hydroxide when dissolved in water and passing through this filter, maybe two or three times for completeness? Guanidine hydroxide just being what guanidine dissolved in water naturally is?
Now thats an interesting one for sure, can I load the column with Ethoxide and run the guanidine.HCl in absolute alcohol through the filter and get the anhydrous base this way?

[Edited on 17-9-2022 by Organikum]

Tsjerk - 17-9-2022 at 08:01

At 25 degrees you can make a 1.6 M solution of potassium acetate in ethanol, which is 16 times more than the 0.1 N acetic acid they advice to use. I would go for that. KCl only dissolves with 0.3 grams per liter. Also you don't have to make the freebase.

[Edited on 17-9-2022 by Tsjerk]

Organikum - 17-9-2022 at 08:13

Quote: Originally posted by Tsjerk

At 25 degrees you can make a 1.6 M solution of potassium acetate in ethanol, which is 16 times more than the 0.1 N acetic acid they advice to use. I would go for that. KCl only dissolves with 0.3 grams per liter. Also you don't have to make the freebase.

[Edited on 17-9-2022 by Tsjerk]

Won't sodium acetate be better, it only dissolves to 0,065g/l in Ethanol whats five times less then KCl? Solubility in Methanol is only 1,31g/l and it makes already such a mess.

I wanted to give the sodium acetate a shot in a small experiment anyways.

thx
/ORG

[Edited on 17-9-2022 by Organikum]

Tsjerk - 17-9-2022 at 12:51

Milk in methanol you say? Couldn't that be freebase guanidine freebase that doesn't dissolve in methanol that well? Even if it would be NaCl, wouldn't you then want another salt to precipitate? Say KCl?

Sure sodium acetate could work, but with potassium acetate you need almost three times less solvent.

[Edited on 17-9-2022 by Tsjerk]

unionised - 17-9-2022 at 14:14

Quote: Originally posted by Organikum

You would need to separate the two resins that are present in the filter or you would probably find that the guanidine bit stuck to the cation exchanger.

And it would probably work better as a relatively long thin column than a typical water filter.

I don't think they work with non-aqueous systems.

it would be interesting to experiment.

Organikum - 17-9-2022 at 23:10

Quote: Originally posted by Tsjerk

Milk in methanol you say? Couldn't that be freebase guanidine freebase that doesn't dissolve in methanol that well? Even if it would be NaCl, wouldn't you then want another salt to precipitate? Say KCl?

Sure sodium acetate could work, but with potassium acetate you need almost three times less solvent.

[Edited on 17-9-2022 by Tsjerk]

Thanks for the very helpful suggestions!

I will actually reduce the solvent volume even more and add the salts, guanidine.HCl and sodium acetate in portions. The only thing I have to find out is the solubility of guanidine acetate in EtOH, what I should be able to determine by experiment myself soon, my first try did not work as planned but it is also not a complete writeoff and some guanidine acetate will be available.

And yes in methanol it will get like milk, the formed NaCl crystals are so tiny. I talked to some people and it seems I am not the first one to make this experience.

Of course if somebody wants to create NaCl nano-particles - thats the way to go obviously.

regards
/ORG