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ssdd
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Most Grignards will start with a bit of moisture if, as pointed out, a tiny tiny amount of iodide is present. Also it is good to have ground your
magnesium turnings in a mortar before hand so the oxide layer is removed and it will react more readily (sometimes the iodide is unneeded if this is
done right).
For all the Grignards I have done I have used an excess amount of magnesium. You will find that most of the time the extra turnings floating around in
solution are no problem and can be decanted off when the reaction is complete. (If you want to do this depends on how valuable your starting reagent
is to you.)
Also to kill the reaction (be sure to let it reflux some after all of the second reagent is added) isopropyl alcohol can be added, but add it slowly
as it reacts with the left over grignard in a mildly reactive way. This is good if you don't want to evaporate off or separate water.
You may want to wash the ether with water several times to remove all of the Mg(Br)OH from the solution (this is a off white crystalline compound that
forms after adding the alcohol or water.)
Hope some of these tips help, they have worked for the tens of grignards I have run in research so they should work.
-ssdd
[Edited on 12-10-2008 by ssdd]
All that glitters may not be gold, but at least it contains free electrons.
-- John Desmond Baernal
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Cobray82
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I have a solution of phenylmagnesium bromide 3M in diethyl Ether.How many (moles) of this solutions equal a solutions of PhMgBr prepared from 79 g.
bromobenzene-.12.3 g. magnesium turnings and 200 ml diethylether.Thanks for your answer
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kristofvagyok
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Quote: Originally posted by Cobray82  | | I have a solution of phenylmagnesium bromide 3M in diethyl Ether.How many (moles) of this solutions equal a solutions of PhMgBr prepared from 79 g.
bromobenzene-.12.3 g. magnesium turnings and 200 ml diethylether.Thanks for your answer |
Fck that. Minimal chemistry knowledge should be in those people who mess with things like this.
1mole PhBr is 157g. What do you think, how much would be the 79g be? -the answer: slightly more than a half mole will be in 200cm3 what will be equal
with 155cm3 of the previously described solution....
But back to the original topic: I heard that PhMgBr could be prepared by a way from PhBr and Mg metal without solvent. They also used this method in
the chem. industry...
Anyone have ever tried it? How much biphenyl comes out by this route?
[Edited on 28-5-2012 by kristofvagyok]
I have a blog where I post my pictures from my work: http://labphoto.tumblr.com/
-Pictures from chemistry, check it out(:
"You can’t become a chemist and expect to live forever." |
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Organicus
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I carried out a Grignard to produce Diphenylmethanol some time ago and documented it very well. There are even youtube videos of the process. =)
Original Link:
http://www.versuchschemie.de/htopic,15266,diphenylmethanol.h...
English translation by google:
http://translate.google.de/translate?sl=de&tl=en&js=...
Hope this will help someone.
best regards
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