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Topic: retrieveing esters?  (Read 5897 times)

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kumarentran

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retrieveing esters?
« on: June 14, 2004, 04:07:39 AM »
i have a mixed solution of the ester i synthesied and the ethanol solution.
i need to extract the ester from the mixture.
i tried levelled distillation under reflux but both compounds distill at the same tempreature.
is there anyway of extracting it?
the H2O formed in the esterification too poses a problem.
how do i get the ester at the purest form to run NMR?

Offline Mitch

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Re:retrieveing esters?
« Reply #1 on: June 14, 2004, 08:12:39 PM »
perhaps several extractions with methylene chloride will do the trick.
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Offline AWK

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Re:retrieveing esters?
« Reply #2 on: June 15, 2004, 07:01:13 AM »
Ethyl acetate is very difficult to obtain in pure form.
For NMR, it should be synthesized from acetic anhydride and ethanol, then it can be purified by distilation using Vigroux column.
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Doxorubicin

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Re:retrieveing esters?
« Reply #3 on: June 30, 2004, 11:48:13 PM »
What is the acid portion of the ester!?!?

I'll just assume you are trying to separate ethanol from ethyl acetate.  

If it were my expt, I would simply add more anhydrous acid and perhaps an inert solvent like benzene or toluene.  Reflux and remove the water via azeotropic distillation.  Distill your product and dry it over anhydrous  potassium carbonate, distill it again through a column..

Sure makes Sigma's prices seem not so bad after all..

cfthb

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Re:retrieveing esters?
« Reply #4 on: July 14, 2004, 04:54:21 PM »
Not knowing the acid you're using, it's hard to answer the question.  But, the best way to make clean esters, with no water problems, is to first make the acid chloride and then CAREFULLY add it, with ice-bath cooling, to the alcohol.  It'll give off lots of HCl gas (do it in the hood), but when you're done, a simple distillation should give you stuff that's very pure.

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Re:retrieveing esters?
« Reply #5 on: July 20, 2004, 02:39:31 PM »
Supposing your product ester is fairly high boiling, you could dissolve your sample in ethyl acetate, wash with water to remove the H2O and EtOH impurities (EtOH is very soluble in water), then wash with brine to dry the organic layer.  Separate the organic layer and dry it briefly over Na2SO4 and then strip of the ethyl acetate.

This wouldn't work if your product ester is low boiling though.  You could probably substitute a different organic solvent though, such as methylene chloride or diethyl ether.  Those boil much lower than ethyl acetate.

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