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Chemistry Forums for Students => Organic Chemistry Forum => Organic Chemistry Forum for Graduate Students and Professionals => Topic started by: animanga008 on June 05, 2010, 02:10:42 AM

Title: How to extract HMPA?
Post by: animanga008 on June 05, 2010, 02:10:42 AM

Hey guys,

I'm currently doing an experiment where I mix HMPA with benzene and nBuLi to deprotonate a molecule. During the extraction process I wash with water and ethyl ether. Now my question is, how come HMPA does not stay in the water layer? With HMPA being so polar, should water hold on to it much stronger then ether? I've run a crude NMR on the ether layer and I always find HMPA no matter what volume of brine i use to wash.

Thanks

Title: Re: How to extract HMPA?
Post by: OC pro on June 05, 2010, 04:42:15 AM

It dissolves good in water and also diethyl ether. The trick is to wash the combined organic layers (after three extractions with e.g. diethyl ether) two times with brine. That should remove most of the HMPA. Trace amounts will then be removed with column chromatography.  

Title: Re: How to extract HMPA?
Post by: Doc Oc on June 05, 2010, 12:13:32 PM

I like the brine idea best, but if that doesn't work you may be able to do a couple of 1M HCl washes, that should be enough to protonate the amines and get them into the aqueous layer.  Depends on whether your product has amines on it too though, could get a little dicey if you do.