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.