From: Olga Tšubrik (olga7$##$ut.ee)
Date: Fri Mar 24 2000 - 13:19:14 EST
Dear Colleagues,
I hope somebody can give me a good advice for my problem.
I synthesized butyllithium by reacting BuCl with excess Li (seven hours
boiling in dry hexane). Then I let the solid phase to settle and
then I siphoned the solution with the argon pressure to the
dry flask. The solution is clear.
All the procedure was done in oven-dried apparatus with dry inert gas
flow (Ar). But now I have a problem with the determination of the BuLi
concentration. I did it twicely.
1. Firstly I hydrolyzed the aliquot of BuLi
by some water and then I titrated it with HCl. I got 1.76M for the
concentration.
2. Secondly I did the so named "double-titration". I react BuLi with
benzylchloride in ether (five minutes for reaction). BuLi must react
with PhCH2Cl and the impurities will remain (BuOLi, LiOH).
Then I decomposed the mixture with water and titrated it with HCl. Now I
got 0.60M for the impurities concentration and so only 1.16M for the BuLi
concentration. Is it possible I have so many impurities in my reagent?
(It means that air humidity and oxygen reacted with the product!)
What do you think about such "double-titration method"?????
Can I trust this method? Or can somebody advice me something better?
All the reagents were pure and dry.
Can someone give me some ideas and suggestions? Help!
Thank in advance.
Olga Tshubrik
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