Sciencemadness Discussion Board

Recrystalizing ammonium methyl sulfate?

LD5050 - 11-6-2017 at 19:44

I made some ammonium methylsulfate by refluxing MeOH and sulfamic acid. I now have a really crude dirty product as some of the sulfamic acid charred in the process. I now am looking to find a way to purify it by recrystalization but I can't find any info on this Chem. Does anyone know what I could use for solvent?

JJay - 11-6-2017 at 21:00

That's going to be tricky even without any charring... if it's charred, I'd suggest just scrapping it and starting over... you're probably looking at ammonium sulfamate, sulfamic acid, ammonium methyl sulfate, and possibly even methylamine and bisulfate and/or sulfate salts at this point... who knows, maybe even [bi]sulfites and/or dimethyl sulfate... you can heat the reaction with a boiling water bath, so there is absolutely no reason to tolerate any charring.

LD5050 - 11-6-2017 at 21:31

The problem was the sulfamic acid wouldn't dissolve it ended up taking around 4 hours to completely dissolve at a strong reflux and initially the stir bar wouldn't spin and in that time some of the sulfamic acid charred i should have kept a closer eye but I didn't, I decided to still go on with synthesis hoping I would still get desired product...

JJay - 11-6-2017 at 21:43

I haven't tried this, but I think you can remove sulfamate from the reaction product between sulfamic acid and methanol by dissolving in water, stirring with an excess of finely powdered barium carbonate, and filtering. After that, I am pretty sure you can evaporate off the water and recrystallize from methanol, but the product might contain some barium... you could probably remove that by recrystallizing from dilute ammonium hydroxide.

If it's charred, though, all bets are off because it will be very difficult to separate the ammonium methyl sulfate without destroying the methyl sulfate ions.



[Edited on 12-6-2017 by JJay]

JJay - 7-9-2018 at 00:09

Quote: Originally posted by JJay  
I haven't tried this, but I think you can remove sulfamate from the reaction product between sulfamic acid and methanol by dissolving in water, stirring with an excess of finely powdered barium carbonate, and filtering. After that, I am pretty sure you can evaporate off the water and recrystallize from methanol, but the product might contain some barium... you could probably remove that by recrystallizing from dilute ammonium hydroxide.

If it's charred, though, all bets are off because it will be very difficult to separate the ammonium methyl sulfate without destroying the methyl sulfate ions.



[Edited on 12-6-2017 by JJay]


I was just researching the best way to make potassium methyl sulfate, and I ran across this old post. This doesn't work; barium sulfamate is too soluble.