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Topic: Grignard reagent and ester reactions  (Read 6156 times)

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Offline hillaire

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Grignard reagent and ester reactions
« on: December 12, 2010, 03:42:31 AM »
Hi,

I'm new to organic chemistry so your help would be very much appreciated!

My textbook states that grignard reagents react with esters to yield tertiary alcohols. The example it gave is as follows:

methyl magnesium bromide (GR) + ethyl pentanoate --> 2-methyl-2-hexanol + ethanol

2CH3MgBr + CH3(CH2)3COOCH2CH3 --> CH3(CH2)3COH(CH3)2 + CH3CH2OH

I would be truly thankful if some one could go through each step to get to the product! I am particularly confused as to where the Mg and Br goes? Thanks in advance!

Offline ooosh

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Re: Grignard reagent and ester reactions
« Reply #1 on: December 12, 2010, 03:58:58 AM »
Do you have any your own idea?

cupid.callin

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Re: Grignard reagent and ester reactions
« Reply #2 on: December 12, 2010, 03:57:10 PM »
I agree with ooosh, you must first try the rxn yourself first. still i'm giving little mechanism.

1) O takes pi bond with him, CH3- attacks C with O.

2) -OC2H5 leaves taking pi elec. with him as OC2H5-

3) C=O reforms.

it forms a ketone which is again attacked by grignard to form tertiary alcohol.

tell me if you need help on attack of grignard on ketone.

:)

Offline jake.n

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Re: Grignard reagent and ester reactions
« Reply #3 on: December 13, 2010, 09:56:03 PM »
Looking up Grignard reagents on the net or in your book should give you an idea of where the bromide and magnesium go after the reaction.  As far as mechanism, just remember that Grignards are very good nucleophiles and review your rules for electrophillicity of carbonyl compounds and you should be able to work through it.

Offline bigchamp89

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Re: Grignard reagent and ester reactions
« Reply #4 on: December 17, 2010, 03:29:42 AM »
Looking up Grignard reagents on the net or in your book should give you an idea of where the bromide and magnesium go after the reaction.  As far as mechanism, just remember that Grignards are very good nucleophiles and review your rules for electrophillicity of carbonyl compounds and you should be able to work through it.
theyre also good bases too :)

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