Author Topic: Ketone distillation @ 200+ C okay?  (Read 552 times)

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aleph

  • Guest
Ketone distillation @ 200+ C okay?
« on: November 08, 2003, 04:14:00 PM »
Dare I dream of ketone distillation at merely ~250 mmHG (21" Hg)?  I think temp will run over 200 C.  I ran across some posts saying 200+ degrees C was not a good idea.  Something about ketone breaking down!  That turns a perfectly good dream into a nightmare.  Anyone with experience in this matter care to comment?


jackhole

  • Guest
P2P Distillation
« Reply #1 on: November 08, 2003, 07:25:00 PM »
I have performed multiple distillations of P2P out of a P2P/toluene mixture over several different temperature ranges due to varying vacuum strengths, and temperatures above 160-170 C generated several side-reactions and unwanted byproducts.  Distillations below that temperature down to about 110 C generated the desired ketone that worked great in reductive aklylations.

The P2P distilled and collected over the higher temperature ranges was more viscuous, darker, and resulted in a lower overall yield in an Al/HG by 20-50%.


aleph

  • Guest
Thanks
« Reply #2 on: November 09, 2003, 05:31:00 AM »
Thanks, Jack


hypo

  • Guest
golly gosh!!
« Reply #3 on: November 09, 2003, 01:33:00 PM »
you have to specify _which_ ketone you're talking about!!
unsubstituted P2P is rather stable,
substituted P2Ps tend to polymerise easily.


Chromic

  • Guest
MDP2P
« Reply #4 on: November 09, 2003, 02:18:00 PM »
SWIC has seen MDP2P distilled without a vacuum at 283C (made from oxone and from peracetic routes)... but don't expect the teflon on the stir bar to last for long, ensure everything is very insulated with glasswool (inc. the clamp), and your yields will be down about 10% on the recovery of the ketone...

So by comparison, 200C is rather light heating... but again, make sure you use glass wool insulating everything, including the clamp. The stir bar will be discolored... but not destroyed.

Perferably you want to do it around 100-120C with a column and insulate (if necessary, likely not) with something like fleece.