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Topic: Azeotrope seperation?  (Read 1351 times)

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Offline zsinger

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Azeotrope seperation?
« on: March 26, 2014, 01:43:47 PM »
All,
Here is my situation.  I am going to be creating a gaseous product which is going to be bubbled into [2M] HCl to crystallize as the hydrochloride salt.  Problem……This product creates a nasty azeotrope with good ol' H2O at a constant boiling point of about 53-55ish C, and the crude product comes over way lower at around 20-23C.  According to the paper, reflux time is 16.25 hours.  The paper also says that the azeotrope will come over first, then the desired pure product (not sure how that works).  As the final product is an amine, I will have to make the reaction solution alkaline (adding NaOH) after reflux is complete (pH greater than 11 in this case) to liberate the product.  Any ideas for an effective separation?  As is forum policy, here is mine, although surely flawed in multiple ways:

Let reaction run with long reflux, slowly basify past pH 11, SLOWLY SLOWLY heat to around the CBP @ 55C.  After the reaction starts to heat up past CBP (indicating no azeotrope present?), quickly cool the pot down to allow for the liberation of the free amine at the known BP of the desired product.  I still postulate that the Azeotrope getting bubbled through the [2M] HCl solution will crystallize something…..just not as intensely, obviously, as the pure liberated gaseous product.  Any help is appreciated, as I like to dig out ALL research and nag smart organic PhD's like many of you for advice.  (It only took me once to learn my lesson regarding experimentation without 110% prior research).  PM's are fine.
              -Zack
"The answer is of zero significance if one cannot distinctly arrive at said place with an explanation"

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