Sciencemadness Discussion Board
Not logged in [Login ]
Go To Bottom

Printable Version  
Author: Subject: Extractive Distillation
rrkss
Hazard to Others
***




Posts: 193
Registered: 18-12-2009
Member Is Offline

Mood: No Mood

[*] posted on 20-7-2010 at 14:10
Extractive Distillation


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?
View user's profile View All Posts By User
rrkss
Hazard to Others
***




Posts: 193
Registered: 18-12-2009
Member Is Offline

Mood: No Mood

[*] posted on 21-7-2010 at 01:37


Supposedly adding water forms a saddle azeotrope. How would I seperate acetone from chloroform?
View user's profile View All Posts By User
bbartlog
International Hazard
*****




Posts: 1139
Registered: 27-8-2009
Location: Unmoored in time
Member Is Offline

Mood: No Mood

[*] posted on 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).
View user's profile View All Posts By User
rrkss
Hazard to Others
***




Posts: 193
Registered: 18-12-2009
Member Is Offline

Mood: No Mood

[*] posted on 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.
View user's profile View All Posts By User
gardenvariety
Harmless
*




Posts: 41
Registered: 19-1-2010
Member Is Offline

Mood: No Mood

[*] posted on 21-7-2010 at 09:02


Why would it destroy the acetone?
View user's profile View All Posts By User
rrkss
Hazard to Others
***




Posts: 193
Registered: 18-12-2009
Member Is Offline

Mood: No Mood

[*] posted on 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]
View user's profile View All Posts By User
gardenvariety
Harmless
*




Posts: 41
Registered: 19-1-2010
Member Is Offline

Mood: No Mood

[*] posted on 21-7-2010 at 09:46


So you expect it would make propene?
View user's profile View All Posts By User
kclo4
International Hazard
*****




Posts: 915
Registered: 11-12-2004
Location:
Member Is Offline

Mood: No Mood

[*] posted on 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.






View user's profile Visit user's homepage View All Posts By User
Sedit
International Hazard
*****




Posts: 1939
Registered: 23-11-2008
Member Is Offline

Mood: Manic Expressive

[*] posted on 21-7-2010 at 20:19


What about a dilute bisulfite wash? remove the ketone while leaving the chlorocarbon.




Knowledge is useless to useless people...

"I see a lot of patterns in our behavior as a nation that parallel a lot of other historical processes. The fall of Rome, the fall of Germany — the fall of the ruling country, the people who think they can do whatever they want without anybody else's consent. I've seen this story before."~Maynard James Keenan
View user's profile View All Posts By User
rrkss
Hazard to Others
***




Posts: 193
Registered: 18-12-2009
Member Is Offline

Mood: No Mood

[*] posted on 22-7-2010 at 03:46


Quote: Originally posted by kclo4  
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.

http://books.google.com/books?id=2idAAAAAYAAJ&pg=PA878&a...

[Edited on 7-22-10 by rrkss]
View user's profile View All Posts By User

  Go To Top