water in acetone

[Eric Lucas]

Acetone is very difficult to get rigorously anhydrous. Many
dehydrating agents actually *increase* water content in
simple ketones like acetone and MEK, as they are generally
either acidic or basic and catalyze aldol condensations that
generate water. I'm not certain about an azeotrope, but
from personal experience, distillation (through a 2' Vigreux
column packed with glass helices) doesn't work--the stuff
comes through soaking wet. The tight-wad I did undergrad
research for insisted the group distill and reuse its wash
acetone. For all the fire hazard this presented (something
like 10 6-liter stills in the group), the glassware washed
with the distilled stuff took hours to dry; that washed with
the fresh stuff dried in minutes.

Check Perrin, Perrin and Armarego's "Purification of
Laboratory Chemicals". They have recommendations, which I
have long since forgotten (because I have long since given
up the foolhardy excercise of using acetone with highly
water-sensitive reagents.) Just a guess, but I might
suggest thinking about drying it over activated 3A molecular
seives or passing it down a column of activated neutral
alumina.

Eric Lucas

jason hathaway wrote:

> Hello,
>
> How would one make acetone anhydrous?
> Simple distilliation?
> Is an azeotrope formed (hi or low BP)?
> Any dehydrating agents?
>
> Thanks,
>
> Jason
>
> ______________________________________________________
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[Jeffrey Bodwin]

-:jason hathaway wrote:
-:>
-:> How would one make acetone anhydrous?
-:> Simple distilliation?
-:> Is an azeotrope formed (hi or low BP)?
-:> Any dehydrating agents?
-:

How dry do you need it and what are you going to use it for? I distill
acetone off of potassium carbonate and that gets it good enough for the
reactions I do, however I'm not using anything that's terribly water
sensitive, I just need to get the acetone dry enough that the slurry of my
reaction doesn't clump up.

If you're looking for azeotropes, find a CRC handbook. There's a table
with a lot of common solvent azeotropes somewhere in there.

Good luck.

--------------------------------**--------------------------------
| Jeffrey J. Bodwin I got lots of good ideas, I just |
| bodw...@umich.edu ain't in charge. - Gallagher |
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