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Chemistry Forums for Students => Undergraduate General Chemistry Forum => Topic started by: 2moles on May 26, 2009, 05:47:21 AM

Title: Grignard reaction on ester - stereochemistry
Post by: 2moles on May 26, 2009, 05:47:21 AM

Hi!

I have a question here... I have an ester reacting with 2 moles of CH3MgBr. I know my product is a tertiar alcohol, but how is the stereochemistry? Is it possible to know whether it is the R or S configuration? Or doesn't this matter since the two methylgroups are the same?

A bit confused..

Thanks if you answer :)

Title: Re: Grignard reaction on ester - stereochemistry
Post by: Arctic-Nation on May 26, 2009, 08:46:03 AM

It does indeed not matter. You can only have a stereocenter with four different substituents, so with your two methyl groups you'll never get enantiomers.

Title: Re: Grignard reaction on ester - stereochemistry
Post by: Loyal on May 26, 2009, 09:40:54 PM

Remember that the Grignard reagent attacks the Ester once which removes the O-R group from the carbon and thus it leaves a Ketone which can react with a second mole of the Grignard.  This means your R-MgCl attaches twice.