Separation of an Ethanol / Pyridine mix

[jmarjorie]

Dear All,

 

How can a mixture of Ethanol and Pyridine be efficiently and totally seperated from the same mix by fractional distillation, which practically yields a constant boiling point mixture of 75 deg Centigrade.

Can both chemical & physical methods be deployed simultaneously ? eg

Can the Pyridine be chemically reacted to form a compound having a much higher boiling point (say with dil HCL, to form Pyridine.HCL ?) or was the distillation temp too high, so that both compounds just distilled over ?

The fractionating column had steel helices and was long enough.

Any suggestions ? Thanks in advance.

[Tartaglia]

Looks like a good candidate for an azeotrope to me. If both pyridine and ethanol are wet (and ethanol will almost certainly be wet unless distilled from sodium) then you will probably have quite a complicated phase system.

[YT2095]

I`ve actualy made several attempts at this in the past and have had varying degrees of sucess, non were 100% though.

I think they knew what they were doing when they decided to add that stuff as a denaturing agent!

NaOH seemed to work quite well and then distilled through activated charcoal, however you`de fair much better with a bottle of over-proof Rum (62.5% alc) or Everclear and distill that

[akcapr]

you could seperate also by taking advantage of the freezing points perhaps

[RyanJ]

Is there not something that can make the Pyridine precipiatate out?

 

If not how about some sort of fractional distillation?

 

Boilling point of Pyridine is 115.2 °C and Ethanol about 78.4 °C thats a difference that can be exploited right?

 

Cheers,

 

Ryan Jones

[akcapr]

ya but they probly form an azeotrope to some extent thats the most obvious method

[RyanJ]

ya but they probly form an azeotrope to some extent thats the most obvious method

 

Thats true and like YT said - they are not idiots, its designed not to be removed...

 

You don't happen to have a centrifuge lying arround do you? I bet you can seperate it out with that but not every home chemist has such equiptment.

 

Are there any proterties of the compound we can exploit?

 

Cheers,

 

Ryan Jones

[akcapr]

centrifuging is hard cuz it can still mix after you centrifuge it

[budullewraagh]

your best bet is to form the hydrochloride salt of pyridine and go from there. make sure the HCl you add is dilute enough so that it does not react with the ethanol to form ethyl chloride. when you're done, convert the PyHCl to the freebase with excess hydroxide.

[jmarjorie]

Thanks everyone for your contribution to this problem. Budullewraagh confirmed the same thought I had; ie empoly a chemical reaction followed by a physical one to seperate the mixtures.....Convert the Pyridine to its hydrochloride, a salt, that has a much higher Bp than the parent compound.

Even though Ethanol & Pyridine have a large difference in the BP, they form a constant BP (azeotrope) mixture....By the way I think its only Conc H2SO4 that will react with Ethanol; not quite sure about dil HCL. Thanks all !

jmarjorie

[jmarjorie]

Thanks everyone for your contribution to this problem. Budullewraagh confirmed the same thought I had; ie empoly a chemical reaction followed by a physical one to seperate the mixtures.....Convert the Pyridine to its hydrochloride' date=' a salt, that has a much higher Bp than the parent compound. Pyridine itself is quite difficult to react chemically.

Even though Ethanol & Pyridine have a large difference in the BP, they form a constant BP (azeotrope) mixture....By the way I think its only Conc H2SO4 that will react with Ethanol; not quite sure about dil HCL. Thanks all !

jmarjorie[/quote']

 

" Impossible is a word in the dictionary of fools "

[Gadolini Rutherfordium]

Using a Dean Stark apparatus, an azeotropic distillation can be done to completely remove the Pyridine. An azeotropic distillation is great for separating azeotropes.