Q on Ochem Destroyer # 97

[bruinguy083]

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I'm really confused about this reaction. In the product, there are four carbons. so the grignard attacks the carbonyl, and i understand how the alcohol is produced, but other than that, i'm lost. can anyone chime in w/ any help? TIA!

 

[nemetrazol]

You have to realize that the grignard reagent in this example is in excess. So 1 mol attacks the carbonyl as you described, forming an alcohol. the other mol displaces the ether group as described in the solutions.
Hope that works.

 

[El Sol]

I'm really confused about this reaction. In the product, there are four carbons. so the grignard attacks the carbonyl, and i understand how the alcohol is produced, but other than that, i'm lost. can anyone chime in w/ any help? TIA!

Grignard reagents add to the carbonyl groups of esters to form ketones; however, these ketones are more reactive than the initial esters and are readily attacked by more Grignard reagent. Two equivalents of Grignard reagent can thus be used to produce tertiary alcohols with good yield.

Whenever you see an ester reacting with a grignard reagent remember that the grignard will attack twice, first through nucleophilic acyl substitution, then through nucleophilic addition.

I hope that helps.