Removing DMF
Anthony James
for way too long. I think maybe the pump needs some attention. Anyone got a
good suggestion for any other good ways to remove DMF - without heating it
up!
Thanks in adavance.
Anthony
Uncle Al
Wash it out with water.
--
Uncle Al
http://www.mazepath.com/uncleal/
(Toxic URL! Unsafe for children and most mammals)
"Quis custodiet ipsos custodes?" The Net!
Menno Deij
wrote:
> I've been trying to remove DMF from a sample oil on a high vacuum manifold
>for way too long. I think maybe the pump needs some attention. Anyone got a
>good suggestion for any other good ways to remove DMF - without heating it
>up!
Hmm... the heating up part is maybe unavoidable, but I've had good
experiences with adding some toluene and rotavapping it to dryness a
few times. DMF seems to disappear with the toluene (I don't know if
there's an azeotrope, but it works ;))
James
DMF can be a real pain. Those twin peaks in the proton NMR are a truly
nasty sight.
I do some condensation reactions in DMF, and find the best way to
remove the solvent is to first rotovap (using a fairly good vac pump
with a dry ice/acetone trap), at between 40-50 oC until no more DMF
comes over and then wash with water or dilute ammonium chloride soln a
few times. This has always worked for me.
Good luck!
Ian Gilmore
A quick pass down a column of silica or alumina sometimes helps. I'd
try UA's wash first-but this should have been done already in a normal
work-up?
If all else fails Kugelrohr at lowish temp/high vac.Maintain your
pumps!
Ian
Ian Gilmore
A quick pass down a column of silica or alumina sometimes helps. I'd
Anthony James
Thanks for your suggestions, if I may return comment.
My product is heat sensitive and acid sensitive, it even has a nasty habbit
of turning into a gel if you add the too much or not enough water.
Given this, not heating was my mantra. Which means adding toluene (b.p. 110
oC) was only going to make my problem worse even if by the time you've
removed the toluene you've got rid of the DMF too.
The solution was working the reaction up in a large excess of water then
extracting into water and washing serval times with water. No DMF and with a
slow removal of solvent a white powder. But the yield is 30%. Some more work
required yet. I'd previously been extracting into DCM.
This little suggestion I got from Advanced Practical Organic Chemistry; J.
Leonard, B. Lygo, G. Proctor; Stanley Thornes Ltd., Cheltenham, UK.
Definately a book worth having a copy of in the lab and recommending to grad
students.
Thanks again.
Anthony
--
Anthony James
=============
W'hoo! DMF free.
Thanks for your suggestions, if I may return comment.
My product is heat sensitive and acid sensitive, it even has a nasty habbit
of turning into a gel if you add the too much or not enough water.
Given this, not heating was my mantra. Which means adding toluene (b.p. 110
oC) was only going to make my problem worse even if by the time you've
removed the toluene you've got rid of the DMF too.
The solution was working the reaction up in a large excess of water then
Ron Jones
Diethyl ether is a poor solvent to use - far too much water solubility
(around 9%), causes mucho partition of your product, not to forget the small
potential problem of peroxides forming. Use t-butylmethyl ether - much
better, and no peroxides.
Ron.
Uncle Al
[snip]
> Diethyl ether is a poor solvent to use - far too much water solubility
> (around 9%), causes mucho partition of your product, not to forget the small
> potential problem of peroxides forming. Use t-butylmethyl ether - much
> better, and no peroxides.
MTBE is an EPA priority carcinogen.