Just made chloroform via the haloform reaction and did my first simple distillation to purify it.
I had the wonderful 80% chloroform 20% acetone azeotrope boil at 64.5 degrees.
I've read that adding water and redistilling the mixture will break the azeotrope and give me 97% pure chloroform.
Can I just add water and distill into a seperatory funnel and then drain the lower layer off for further drying or is there some special technique to
extractive distillation to eliminate the acetone?rrkss - 21-7-2010 at 01:37
Supposedly adding water forms a saddle azeotrope. How would I seperate acetone from chloroform?bbartlog - 21-7-2010 at 05:19
If you add water and distill again you will re-separate the acetone/chloroform from the water, so that seems pointless. I think repeated washes with
small amounts of water would be one way to remove most of the acetone, though some CHCl3 would be lost as well.
In general the way to avoid this is to use stoichiometric amounts of acetone or only a slight excess, and do the initial separation of chloroform and
aqueous products mechanically (pipette, decantation, or separatory funnel). rrkss - 21-7-2010 at 08:44
I'm wondering if I can shake the chloroform/acetone with concentrated H2SO4. That should destroy the acetone and leave the chloroform intact.gardenvariety - 21-7-2010 at 09:02
Why would it destroy the acetone?rrkss - 21-7-2010 at 09:08
Its a strong dehydrating agent.
Edit: Seemed to work, I shook my product with H2SO4, and distilled. The product boiled at slightly under 62 degrees.
[Edited on 7-21-10 by rrkss]gardenvariety - 21-7-2010 at 09:46
So you expect it would make propene?kclo4 - 21-7-2010 at 20:12
Adding H2SO4 sounds like a horrible idea.
Acetone polymerizes into all sorts of different things, and I would expect the chloroform to get taken into the reaction, possibly producing something
dangerous.
Wash it with water a few times, than distill -- or perhaps you can get something that will react with the acetone but not chloroform, just not
something that causes the acetone to seriously change. I know calcium chloride reacts with a lot of alcohols, and I believe it may form some sort of
salt with acetone as well - perhaps look into using the anhydrous calcium chloride as an option?
Might also work to dry it - than upon distillation you'd probably get pretty good chloroform.
Sedit - 21-7-2010 at 20:19
What about a dilute bisulfite wash? remove the ketone while leaving the chlorocarbon.rrkss - 22-7-2010 at 03:46
Adding H2SO4 sounds like a horrible idea.
Acetone polymerizes into all sorts of different things, and I would expect the chloroform to get taken into the reaction, possibly producing something
dangerous.
Chloroform won't react under these acid conditions. By polymerizing the acetone I highly increase its boiling point and can seperate it from the
chloroform.
I got the procedure from a book on preparing chloroform for anaesthesia. It worked as it distilled at pretty much the literary boiling point.
