What aprotic solvents is formic acid soluble in?

[Tremenda]

Dear all,

What solvents is formic acid soluble in?

I am after an aprotic solvent that is less dense than water.

Thanks

[Don_Hilton]

Google the terms "formic acid solubility" and see what shows up. You have a wide selection. (I just checked.)

[Tremenda]

mmm...I am afraid it is not that simple.

Only very polar protic solvents show up, i.e. water and alcohols.

I discovered by testing that it is also soluble in CH2Cl2, but it denser than water.

I need a safe (reasonably high boiling point) aprotic solvent less dense than water...and immiscible with water. (too many things to ask for I think...)

Any ideas?

[HW Mueller]

Ether(s)?

[Tremenda]

I think it is soluble in diethyl ether...but aren't they dangerous?
They form explosives peroxides as far as I know...

[Don_Hilton]

About any polar organic solvent should dissolve formic acid. Depending on the concentration you need, there is some degree of solubility in hydrocarbon solvents. (per Wikipedia)

I see a reference to a 50:50 mixture of formic acid and toluene being used for a reaction. (http://www.jbc.org/content/86/2/695.full.pdf) and other solvents are mentioned.


Diethyl ether can be used with proper precautions for storage - but it is not particularly high boiling.

[tom jupille]

what about acetonitrile?

[Camisotro]

Indeed, ACN comes to mind as well, but "immiscible with water" is the one criterion by which it would fail.

May I ask why you need to locate such a solvent? Intuitively it would seem to me that any solvent non-polar enough to be immiscible with water will be a poorer solvent for formic acid than water. So if you take a solution of FA in that hypothetical solvent and add an aqueous phase, the FA would in all likelihood partition to the water.

[tom jupille]

I missed the "immiscible with water" part.

However, if the object is to extract formic acid from water, what about simply acidifying the water to a pH well below the pKa of formic acid (sulfuric acid should do the trick) and then extracting with methylene chloride?

[HW Mueller]

He also wants a density which is lower than that of water.

[tom jupille]

My brain is apparently on summer vacation. But the principle still stands: drop the pH below 2 to make sure the formic acid is in the free acid form and extract into an organic solvent of choice.