vulture - 26-3-2006 at 12:17
I currently have a lab assignment that requires us to synthesize poly(octyl)thiophene.
Dibromooctylthiophene is reacted with a grignard reagent first at which point grignard metathesis occurs, that is, one bromine on the thiophene
becomes MgBr, essentially making the thiophene a grignard.
However, I can not find the mechanism through which GRIM proceeds and I have a bit of trouble coming up with one myself. If one assumes methylbromide
is produced, that would mean it originates from reaction between a carbokation (from the original grignard reagent) and the bromine anion leaving the
thiophene, but this doesn't seem right to me.
Anybody got a good view on this?
Sandmeyer - 28-3-2006 at 02:23
Maybee this is of some help:
http://www.chem.cmu.edu/groups/mccullough/publication/PDF%20...
vulture - 1-4-2006 at 03:37
I know the article, pretty much describes our lab assignment.
Anyway, the paper does not propose a mechanisme for the GRIM, but only for the polymerization.
turd - 1-4-2006 at 05:30
Who cares, as long as it works? 
http://www.scs.uiuc.edu/denmark/presentations/2005/gm-2005-0...
leu - 2-4-2006 at 04:15
The mechanism is primarily free radical 
turd - 2-4-2006 at 12:58
SET. If you want to be cool, you have to call it SET.
Cloner - 4-4-2006 at 00:58
I think of the halogen atoms in organic molecules as being slightly loose, aka, they are in equilibrium with solvated state. I just changed the
chlorine for iodine in dibenzylchloride by refluxing with KI in acetone, driven by insolubility of KCl. The thiophenes have a 'tighter' bond with
bromine than a benzylbromide has, but less tight than in bromobenzene. The bromine atom merely takes the most stable place out of the equilibrium
while the MgX is there to take its place.