Metacelsus
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Separating chloroacetone from water
I recently made some chloroacetone by electrolyzing a mixture of acetone and hydrochloric acid. After removing the dichloroacetone (insoluble) and
aldol condensation crap, I now have about 500 ml of what I think is a close to saturated (~10 g/ml) solution of chloroacetone in water. I tried
separating it by conventional distillation, but its boiling point is too close (119 C) to that of water and I just got a more dilute solution of
chloroacetone in water. At this point I think I have three options:
1) Fractional distillation. I would need to buy a Vigreux column or equivalent.
2) Liquid-liquid extraction. I would use chloroform as the solvent, because it is the only low-boiling water-immiscible solvent that I can make (by
acetone + NaOCl). I would then distill off the chloroform. I'm not entirely sure that this would work.
3) Using a drying agent. Conceivably, if I dumped a whole lot of anhydrous MgSO4 into the solution, it would lock up all the water and I could distill
off the chloroacetone. I'm also not entirely sure that this would work.
Which method(s) should I try?
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DraconicAcid
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If you add a lot of salt to the solution, it could reduce the solubility of the chloroacetone.
Please remember: "Filtrate" is not a verb.
Write up your lab reports the way your instructor wants them, not the way your ex-instructor wants them.
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Prometheus23
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Chloroform should be a reasonably good solvent for extracting chloroacetone from an aqueous solution. DraconicAcid's suggestion of salting out the
chloroacetone by adding a very water soluble salt also sounds pretty good. If I were you I think I'd try using both methods to get as much of it out
of the water as possible. I would think adding NaCl until basically no more will dissolve will certainly start to push out at least some of the
chloroacetone. If your solution is indeed saturated or close to saturated anyways. Then do a few chloroform extractions, wash and dry the chloroform,
and evaporate to see what you get. Fractional distillation as a final purification step would be ideal obviously.
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macckone
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If the solution of chloroacetone and water is saturated, the first step is to add salt (calcium chloride or magnesium sulfate will work). Then
extract the mixture with ether. The ether can then be evaporate easily giving a reasonably pure product.
Boiling should give a constant boiling mixture of water and
chloroacetone (89C). I wish I had a reference for that temp and
the actual mixture. If anyone has a good reference can they provide it?
Side note, you can get reasonably good purity by just salting out if you have enough chloroacetone in the mix.
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Organikum
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I doubt that calcium chloride will work as drying agent in for wet chloroacetone or a plain mixture of water and chloroacetone. It might produce some
interesting results though.
Salting (out) with NaCl or another very unreactive salt followed by distillation as Draconic said, extraction (but the next separation has to be a
simple one, or azeotropic distillation and removal of water with a suitable carrier, chloroform, DCM, ether come to mind.
Best place to check for azeotropes is here:
http://vle-calc.com/azeotrope.html
a hidden treasure
/ORG
PS: Bromoacetone seems to be the for most purposes same useful reagent and better regarding preparation and handling. Bromine can usually be regained
i the end what levels costs.
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macckone
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Calcium chloride isn't a drying agent.
It is used to give a good separation ie salting out.
Magnesium sulfate also works.
Sodium chloride is less effective in my experience.
With the 10:1 ratio you need an extractant and I recommend
ether because it doesn't form an azeotrope.
I was actually looking for an authoritative reference.
vle-calc.com doesn't have that azeotrope. I know
it exists but I don't have anything authoritative.
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Metacelsus
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I have bromine now; I didn't have it 8 months ago. I would definitely prepare bromoacetone if I needed a haloacetone.
I ended up extracting the chloroacetone with petroleum ether (probably mostly hexanes).
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macckone
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Found the reference for the constant boiling mixture:
The reduction of cupric chloride by carbonyl compounds, Jay Kochi,
J. Am. Chem. Soc., 1955, 77 (20), pp 5274–5278
DOI: 10.1021/ja01625a016
Temp is 89C and mixture is approximately chloroacetone and water
in a 5:1 ratio. More exact measurements are not given. This is mostly
free of 1,1 dichloroacetone as the mixture boiling point is 29C lower
than the dichloroacetone. 1,3 dichloroacetone has a boiling point of
179C.
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softbeard
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Would chloroacetone form an addition product with sodium bisulfite like acetone? Maybe the addition product would be easier to separate. I don't see
chloroacetone reacting with aqueous sodium bisulfite, but you would have to adjust the pH and neutralize most of your hydrochloric acid.
Just realized OP asked this question over 2 years ago!
[Edited on 18-8-2015 by softbeard]
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macckone
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Yes, it would form an addition product provided you had the correct pH. Given that acetone and chloroacetone form polymers if left in acidic
solution, you would need to adjust the pH anyway if you want to recover a product.
On this board it is considered appropriate to continue a thread rather than open a new one.
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