[arborescent]

Hello,
I performed this reaction:
1-(4-bromophenyl)-1-phenylethylene + Mg -->  X
X +Ethylene oxide --> product

I left the 2nd step overnight; the reaction gelified.
What happened?
Let me know if you have an idea....

Thank you very much.

Note: I was able to dissolve the gel after quenching with HCLaq.

[arborescent]

Maybe I will rephrase. Is it a bad idea to add an large excess of ethylene oxide to a Grignard reagent? I read that usually, only 1 or 2 equivalents are added. Can EO polymerize with a Grignard reagent?
Thank you for any opinion.

[macman104]

Yes, EO can polymerize (http://en.wikipedia.org/wiki/Polyethylene_glycol).  Although, I'm not sure if it will polymerize under grignard conditions.  What was the concentration of the EO in the reaction mixture?  You could get an opening of the ethylene oxide, and then if the concentration of the EO was high enough, that anion could attack another molecule of EO and open it.  If it dissolved in HCl it is possible that you did polymerize it, as PEG is soluble in water.

Also, is there a reason you left it stirring overnight?  I have to imagine that reaction is pretty quick, and does not require overnight stirring.

[arborescent]

Yes, I just left it overnight by "lazyness" (I didn't want to wait to quench it). I guess that was a mistake. 
The crude product looks like a viscous oil. I am going to try to purify it and see if any pure product is there along with the supposed PEG polymer.

Thanks a lot for you answer!