Natural Science Forum / Chemistry / Organic Synthesis / February 2004

How dry is "dry?"  Try freshly activated 13X molecular sieves or
Activity 0 basic alumina (but the latter won't remove dimethylamine).

Vacuum distillation (10-50 Torr) from calcium hydride (CaH2). Take the
middle cut. (Recycle the front fraction, do no distill to complete
dryness).

HMPA has been used by enthomologist for sterilising insects - before
they found out that it works the same with people too...

I'll suggest to shake it with 0.1 eq. of CaH2 and then a low pressure distilation.

best regards

André

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Sieves are the only really good way to dry HMPA, make sure the sieves are REALLY dry!  Flame them under high vaccuum.

In case you don't know HMPA is a really bad carcinogen.  I know everything  is blah blah, but HMPA is really bad.
It causes cancer in mi
ce on the nanogram exposure level.  I would suggest avoiding HMPA entirely, there are many alternatives.

Nate

ttp://organicworldwide.net/sci.chem.organic.synthesis

For a quick and simple way we just vacuum distill from Calcium
hydride, then store over molecular sieves (3A).  Seems to produce dry
enough material for our use (tBuLi amongst others).

James