buuun
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Can 2-chloroethanol be prepared with glycol + HCl(aq), rather than HCl gas?
I was wondering if there's an alternative that doesn't require a gas generator.
By looking at the equation, there's no apparent reason why it'd need to be anhydrous, in fact, the reaction forms water as well, and the product is
stable in water.
So, is there any reason not to do it this way?
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DraconicAcid
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I suspect it's an equilibrium reaction which is acid-catalyzed, or at least one of the steps in the reaction can be reversed by the addition of water.
If it doesn't work with aqueous hydrochloric acid, you might be able to get it to work with a high concentration of calcium chloride in addition to
the acid.
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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buuun
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Quote: Originally posted by DraconicAcid  | | I suspect it's an equilibrium reaction which is acid-catalyzed, or at least one of the steps in the reaction can be reversed by the addition of water.
If it doesn't work with aqueous hydrochloric acid, you might be able to get it to work with a high concentration of calcium chloride in addition to
the acid. |
Huh, makes sense. Assuming CaCl2 doesn't work, would dry zinc chloride be possible? Analogous to the preparation of alkyl chlorides?
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zed
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You can probably do it with aqueous HCl, but generating HCl gas is pretty easy.
And, quite importantly, I'm guessing that you already have an outline of the gassing procedure.
No point in reinventing the wheel, when you have such a simple procedure already.
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buuun
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| Quote: Originally posted by zed | You can probably do it with aqueous HCl, but generating HCl gas is pretty easy.
And, quite importantly, I'm guessing that you already have an outline of the gassing procedure.
No point in reinventing the wheel, when you have such a simple procedure already. |
Right, but a reaction between the two liquids would allow to just autoclave it for a couple of hours, which seems like a more convenient and elegant
solution.
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CuReUS
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| Quote: Originally posted by buuun | | Assuming CaCl2 doesn't work, would dry zinc chloride be possible? Analogous to the preparation of alkyl chlorides? |
yes
A better way to make chloroethanol is to react epoxide with HCl
https://en.wikipedia.org/wiki/Ethylene_oxide#Halide_addition
[Edited on 17-9-2016 by CuReUS]
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Darkstar
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The reason it needs to be anhydrous is because 2-chloroethanol forms an azeotrope with water. The azeotropic mixture consists of nearly 60% water and
boils at just under 100 °C, making it impossible to separate with simple or fractional distillation. (it may be possible to separate under a vacuum,
however) So unless you're after a dilute aqueous solution of 2-chloroethanol, your reaction conditions will need to be as dry as possible.
Now with that said, I have heard that the azeotrope can supposedly be broken through chemical means using anhydrous sodium sulfate. The
azeotropic mixture is heated to 32 °C to maximize solubility, and then dry sodium sulfate is added until the solution becomes completely saturated.
After the remaining undissolved sodium sulfate has settled, the supernatant is then decanted off and allowed to slowly cool to room temperature. A
small amount of sodium sulfate decahydrate is then added to serve as a seed crystal and the supersaturated solution is allowed to slowly crystallize.
The mixture finally separates into two phases, and the upper 2-chloroethanol layer is then separated, dried and redistilled to obtain nearly pure
2-chloroethanol.
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