yoyoils
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Azeotrope question
I'm wondering IF when isolating methanol from a solution of nitromethane in methanol, (using distillation) would you be able to obtain pure methanol?
because I've read how they form an azeotrope, but I gotta be sure the methanol I save wont contain any trace nitromethane. At All
[Edited on 15-4-2012 by yoyoils]
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weiming1998
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If you've read that they form an azeotrope, and what the book says is true, then you cannot separate them by distillation using conventional methods.
The only 2 ways I could think of is to either react the nitromethane with something that won't react with ethanol, or make an ester of an acid with
methanol, distil the ester/nitromethane away, then hydrolyze it back into methanol and the corresponding salt using a base.
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yoyoils
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I know distilling nitromethane from methanol, i'll always will result a mixture no matter how i try but can you distill pure methanol and leave all
the MeNO2 behind??
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weiming1998
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Quote: Originally posted by yoyoils  | | I know distilling nitromethane from methanol, i'll always will result a mixture no matter how i try but can you distill pure methanol and leave all
the MeNO2 behind?? |
I don't know what you mean by that. Why would you need to distil pure methanol? And if you are distilling pure methanol, why would it leave behind
nitromethane? As I said before, ordinary or fractional distillation does not work for a mix of methanol and nitromethane, no matter what order you
distil in or how many times.
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Magpie
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| Quote: Originally posted by yoyoils |
I'm wondering IF when isolating methanol from a solution of nitromethane in methanol, (using distillation) would you be able to obtain pure methanol?
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You have told us that there is a methanol/nitromethane azeotrope. But you have not told its concentration, its bp, the bp's of methanol and
nitromethane, nor the methanol concentration of your starting solution. We can't answer your question without this information. Are we supposed to
look all this up?
[Edited on 16-4-2012 by Magpie]
[Edited on 16-4-2012 by Magpie]
The single most important condition for a successful synthesis is good mixing - Nicodem
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Organikum
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Apply reduced/elevated pressure and/or ternary azeotropes for separation.
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fledarmus
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Methanol (bp 64.7C) and nitromethane (bp 101.2C) form a low boiling azeotrope (bp64.6C) containing 9% nitromethane. Wikipedia, Azeotrope(data)). This means that when you try to distill a mixture of nitromethane and methanol, the lowest boiling fractions that you
collect will be those containing 9% nitromethane. If you start with a solution that contains less than 9% nitromethane, you will collect pure methanol
once all the nitromethane has been removed as a 9% solution in methanol; if you start with a solution that contains more than 9% nitromethane, you
will collect pure nitromethane once all the methanol has been removed as a 9% nitromethane solution.
The boiling points of the azeotrope and the pure methanol are so close together that it would be very difficult to tell when all the nitromethane was
gone and you were collecting pure methanol.
You could add cyclohexane to your mixture and boil off an even lower boiling azeotrope (54.2C) containing 62.8% cyclohexane. Then a water extraction
will remove the methanol from the cyclohexane, and a final distillation of the methanol from water will give you pure methanol.
Reducing the pressure will change the boiling points of all the components of the mixture, but will not change their rank order. You still won't get
any pure material, only the azeotrope at a lower temperature.
[Edited on 17-4-2012 by fledarmus]
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