Sciencemadness Discussion Board

drying EtBr for grignard

jwarr - 1-9-2011 at 19:34

Whats the best way to dry EtBr for a grignard reaction? I figured I would just dry it over sodium sulfate anh. then transfer via a canula to a flame dried argon flushed flask. Would this be sufficient?

TerryFlamingo - 1-9-2011 at 21:33

Why not dry it directly over magnesium metal in the presence of dry nitrogen, followed by the addition of the other reagent you are forming the adduct with, followed by acid treatment. Should save you the cost of argon, as well as the potential hazard of moisture getting in during transfer.

drago57 - 2-9-2011 at 07:36

You could pass it through a short plug of alumina if you've got that to hand.

But depending on exactly what you're trying to do, I'd be tempted to give it a go first without worrying too much about perfectly dry conditions (though dry solvent is always necessary) and only get into that if you can't get it to work. The 1st year undergrads at uni (not a species renowned for their riogorous lab technique!) do a Grignard in their lab course and of the 100 or so in each year only 1 or 2 fail to get it to go 1st try.

smaerd - 2-9-2011 at 07:50

I've never done this before, so I can't tell you this is the way. So perhaps my post is irrelevant.

Though I don't see why you couldn't dry it in CaCl2 than either distill, or maybe dry with CaCl2 and follow up with MgSO4(anhydrous).

chemrox - 2-9-2011 at 21:39

drying it over MgSO4 should be sufficient for a Grignard. Might even be overkill. Main thing with a Grignard is getting wet vapor out of the apparatus by flaming it first. Never had trouble with one.