basic organic synthesis

[crimsonpetal]

VŒš Microsoft Word •¶žƒ.dochello, today I went over a ppt about organometallic compounds and I found I can't figure out why this equation could happen, can someone

help me ?

[Titan1290]

This might be a little too basic I don't know much chemistry but from what I can see it looks like water has been removed leaving a phenyl group linked to the benzene ring with 2 carbons and a hydroxyl group left off the ring. The hydroxyl is negatively charged could it be attracted more towards the benzene due to bond enthalpies/charge. Hope more people comment a chemist will be able to answer this better than me.

[BabcockHall]

I would analyze it in terms of carbons that have a partial positive charge or a partial negative charge.

[Knumbnuts]

You have gone from a 6 membered ring to a 5 membered ring upon reaction with benzylmagnesium bromide! Is this an error? I ask because the Grignard reagent will open the epoxide ring.

 

On a side note how does one attach an image to a post?. If it was obvious then I would have posted the reaction I am talking about.

Thanks for any clues to this.

[Knumbnuts]

OK, I sorted it out. It taught me to scan down the page!

Here is what I am talking about in the above.

 

epox.tiff

[BabcockHall]

LOL, I assumed that the Grignard would open the epoxide, but I managed not to see the question of ring size at all. I also have to wonder whether or not this is an error of some kind.

[crimsonpetal]

OK, I sorted it out. It taught me to scan down the page!

Here is what I am talking about in the above.

 

okay, I find the explanation finally. Since magnesium halides are moderate Lewis acids,their presence in solution may influence the outcome of certain chemical reactions. Magnesium bromide rearranges the epoxide to cyclopentanecarbaldehyde, which then adds the Grignard reagent in the expected manner like your drawing. dialkylmagnesium reagents and organolithium reagents simply adds to the epoxide by opening the strained ring, they are more selective. For the mechanism of the rearrangement, I am not sure, I think it may like the pinacco rearrangement.