I have a mixture of ethyl acetate, water and isopropanol that needs separating, but I cannot ascertain how to achieve this.
I have removed the water component by drying the mixture over anhydrous calcium chloride with magnetic stirring, which eliminated the water content
(tested with anhydrous copper sulfate and calcium carbide), leaving the iPrOH and EtOAc behind. However, to my knowledge, these form an azeotrope at
75.3*C (see Wiki article on azeotrope data) and atmospheric normal and fractional distillations verified this.
This patent suggests that extractive distillation can be used to separate isopropyl acetate and isopropanol, and I assume a similar technique can
be employed here. However, I do not possess the extractive solvents they describe (" a mixture of a polyol and one or higher boiling oxygenated,
nitrogenous and/or sulfur containing organic compounds; typical examples of effective agents are 1,3-butanediol and dimethylsulfoxide;
1,2,6-hexanetriol, dimethylsulfoxide and dimethylformamide.")
Any suggestions?
Thanks in advance.
If it is of any concern, the EtOAc will be employed in a Claisen condensation using sodium metal (where the presence of iPrOH would cause the
formation of sodium isopropoxide as opposed to the target product). An initial thought I had was to use sacrificial sodium to scavenge the iPrOH, but
I have a mere 10g of the Na and do not wish to waste it. I also thought of adding a mild oxidizing agent (acidified dichromate?) to oxidize the iPrOH
into acetone, leaving the ester untouched (not easily oxidized)...does acetone form an azeotrope with EtOAc?
[Edited on 1-1-2013 by Hexavalent]Siggebo - 1-1-2013 at 10:09
The wikipedia data sheet for Azeotrope does not list an acetone/ethyl acetate azeotrope.
If it is of any concern, the EtOAc will be employed in a Claisen condensation using sodium metal (where the presence of iPrOH would cause the
formation of sodium isopropoxide as opposed to the target product).
Why not use the mixture for the Claisen? NaOiPr is as good base as NaOEt, the only side reaction what could happen is that you will probably get
isopropyl-acetoacetate as a product, what could be easily converted back to the ethyl ester if preferred with a simple H+ esterification in ethanol.
If this is not a good option, I would add a lot water, separate the EtAc and dry it... Isopropanol could go to the waste.
Also is there a measured content what percentage of EtAc and iPrOH does the mixture contain?Prometheus23 - 1-1-2013 at 12:18
Could you not add the mixture to a large volume of water and separate the EtOAc? Isopropanol will partition between the water and EtOAc layers but it
should mostly go into the aqueous phase. Do this a couple times and then dry the EtOAc.
Also I was under the impression that you could not dry alcohols with calcium chloride.Hexavalent - 1-1-2013 at 12:20
Unfortunately not, although data for the azeotrope composition is available.
I didn't think of using the NaOiPr as an alternative base, actually, and some EtOH is usually added anyway to form NaOEt. I guess, in this instance,
it could be omitted due to the presence of the NaOiPr.
I'll try the first idea, and report back...BTW, what do you mean by 'esterification'? Taking the crude acetoacetate product, and refluxing with
ethanol over H2SO4, for example?Hexavalent - 1-1-2013 at 12:28
