Re: ORGLIST: Preparing LDA

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From: Ohad Ilovich (ilovich$##$pob.huji.ac.il)
Date: Tue Jan 30 2007 - 01:37:34 EST


Just a couple of things i remeber from preparing this myself after my
advisor insisted as well.....
Use freshly distilled (over sodium) dry THF and freshly distilled
diisopropylamine (over calcium hydride) to make the starting solution. Cool
to -78 and then slowly add the n-BuLi to the mixture while keeping the temp
under -65.
I didn't store it but made it fresh for each reaction. I had no workup but
rather just added the reactants to this solution (i also some articles in
which they injected this solution onto another).
The first time will take a little getting used to but afterwards it'll be a
walk in the park
Good luck,
Ohad

----- Original Message -----
From: "Ken Knott" <esprcorn$##$hotmail.com>
To: <everybody$##$orglist.net>
Sent: Monday, January 29, 2007 12:54 PM
Subject: ORGLIST: Preparing LDA

>
> My advisor would like me to prepare LDA rather than buy it due to its poor
> shelf life.
>
> I've been able to figure out this much, LDA is prepared from a reaction
> between n-butyllithium and diisopropylamine at -78C under nitrogen.
>
> Couple questions, 1) Is the best way to do this to prepare two flasks and
> cannulate the diisopropylamine over into the n-butylithium?
> 2) I assume the byproduct butane is inconsequential as I've never seen
> any
> mention to a work up removing it.
> 3) In fact I've seen no workup whatsoever. Is is ready to go once made?
> 4) Can you assume complete conversion when determining molarity of the
> product?
> 5) Anything else I should be aware of regarding storage, use, workup,
> preparation?
>
> I'm a first year grad student... Getting my feet wet.
>
> Thanks,
>
> Ken
>
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