Sciencemadness Discussion Board

Extraction of fumaric acid

ChemLlama - 31-12-2015 at 01:50

Hello all! I'm new to these forums, nice to meet all of you :)

I have some iron(II) fumarate tablets, and I'd like to convert it to fumaric acid. I was thinking about acidifying it in solution, but unfortunately according to this link, it has a measly solubility of 1.4 g dm-3 in water at 25oC, while fumaric acid has a solubility of 6.1 g dm-3. Since the reactant has a lower solubility in water, but not a significantly low enough to achieve a clean separation of fumaric acid and the reactant, what else can I do to obtain fumaric acid? I can't seem to obtain data about the solubilities of these two compounds in different solvents except that iron(II) fumarate is "very slightly soluble" in ethanol and that fumaric acid has a solubility of 54.4 g dm-3 in 95% ethanol according to this MSDS.

Provided that I have water, ethanol, toluene, ethyl acetate, hexane, and small amounts of isopropanol and acetone as solvents, how should I carry out the extraction and purification of the fumaric acid? Thank you!

Tsjerk - 31-12-2015 at 06:15

Assuming fumaric acid is heat stable (at least at boiling water temperatures), maybe you can add iron(II) fumarate to water to an amount that would give around 6 grams/liter of the acid. Then acidify with HCl, around 3 molar equivalent (1.5 times the needed amount). The acid will dissolve, and water can be boiled away making crystallization of fumaric acid possible.

FeCl2 and FeCl3 will stay in solution and excess HCl will evaporate off. Washing can be done with cold water as fumaric acid has a low solubility.

The Volatile Chemist - 31-12-2015 at 16:31

Perhaps make the solution as above, then precipitate it with a barium (or other alkaline earth) salt (this would be best only assuming you have a lot of the fumarate), then acidify with H2SO4 and filter off the highly insoluble BaSO4.
Interesting salt, how'd you acquire it?

blogfast25 - 31-12-2015 at 18:05

Crush the tablets and make a thin slurry with water.

Treat with strong ammonia. This will give highly insoluble Fe(OH)2 and ammonium fumarate, which I assume to be water soluble.

Separate by filtration.

Neutralise the clear filtrate with HCl solution, this will give the poorly soluble fumaric acid and highly soluble ammonium chloride.

Separate by filtration.

Try to always calculate the amounts of reagents used (stoichiometry).


[Edited on 1-1-2016 by blogfast25]

AvBaeyer - 31-12-2015 at 20:15

You worry too much here. Slurry the iron fumarate in water, then add acid (HCl or H2SO4) to pH 1 or so. You will preciptate the fumaric acid and the iron chloride or sulfate will remain in solution. You may have to provide some heat to the reaction to get it to completion. You do not need a lot of solubility of the iron fumarate to get this to work. It's a simple double-decomposition reaction. Keep in mind that the fumaric acid will have greatly reduced solubility in the aqueous acid reaction mixture. Isolate the fumaric acid by filtration and recrystallize it from aqueous acetic acid or other solvent of your choosing.

AvB

ChemLlama - 1-1-2016 at 01:26

Quote: Originally posted by The Volatile Chemist  
Perhaps make the solution as above, then precipitate it with a barium (or other alkaline earth) salt (this would be best only assuming you have a lot of the fumarate), then acidify with H2SO4 and filter off the highly insoluble BaSO4.
Interesting salt, how'd you acquire it?


Hmm, assuming that barium fumarate is insoluble enough to achieve quantitative precipitation, how will it react with aqueous H2SO4 to form the aqueous acid? Wouldn't the BaSO4 just form an impervious coating around the barium fumarate particles?

Oh and I don't have much of the iron(II) fumarate, I think about 4 grams of it or so. I bought it at a pharmacy, it was being sold as an iron supplement :P it says "ferrous fumarate 200mg" and nothing else, so I'm going to weigh a tablet and hope it works out to be 0.2g, which would mean that it doesn't have any fillers. Those would be troublesome to remove since I wouldn't know its identity...

[Edited on 1-1-2016 by ChemLlama]

ChemLlama - 1-1-2016 at 01:30

Quote: Originally posted by AvBaeyer  
You worry too much here. Slurry the iron fumarate in water, then add acid (HCl or H2SO4) to pH 1 or so. You will preciptate the fumaric acid and the iron chloride or sulfate will remain in solution. You may have to provide some heat to the reaction to get it to completion. You do not need a lot of solubility of the iron fumarate to get this to work. It's a simple double-decomposition reaction. Keep in mind that the fumaric acid will have greatly reduced solubility in the aqueous acid reaction mixture. Isolate the fumaric acid by filtration and recrystallize it from aqueous acetic acid or other solvent of your choosing.

AvB


Hmm... Thank you, I'd consider that method :) Do you think the best way to purify the resultant precipitate which likely contains the iron(II) salts and the fumaric acid I want to obtain is to dissolve it in 95% ethanol, filter, and evaporate the filtrate? Thanks!

Happy New Year to everyone by the way :D

The Volatile Chemist - 6-1-2016 at 13:39

Sorry, I guess I was assuming fumaric acid could be distilled, just had to look at its structure and realized that wasn't so. AvBaeyer's method should work.