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Topic: ButylLithium, THF, and H2O  (Read 9873 times)

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Offline Aznhmonglor

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ButylLithium, THF, and H2O
« on: March 25, 2009, 08:35:55 PM »


Alright so there's the problem, What I tthought it would make:



What am I doing wrong here?

Offline wanderlust

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Re: ButylLithium, THF, and H2O
« Reply #1 on: March 25, 2009, 10:08:22 PM »
Ah, I'm no expert but I believe this is a case of conjugate addition.  Without the double bond in the cyclohexane you would generate a tertiary alcohol but since you have a conjugated system you actually see addition of your nucophile at the third position and the retention of your keytone. 

I hope this helps.  Maybe someone with more experience can verify this or help you further. 

Offline Aznhmonglor

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Re: ButylLithium, THF, and H2O
« Reply #2 on: March 25, 2009, 10:17:56 PM »
Hmm what do you mean my nucleophile adds to the third position? so it would look something like this???


*Ketone at the top there, forgot to put the oxygen.

Not sure if I attacked the BuLi in the right place but right concept now?

Offline wanderlust

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Re: ButylLithium, THF, and H2O
« Reply #3 on: March 25, 2009, 10:32:52 PM »
No, counting your keytone as the first position and counting clockwise (you're missing your oxygen, btw) you would add butyl to the third position and remove the double bond.  The reaction mechanism is somewhat complex and ends up with a negative charge on the second carbon which grabs a hydrogen. 


In the end you have....(deep breath, it's been awhile for nomenclature) 3-butylcyclohexanone? 

http://en.wikipedia.org/wiki/Conjugate_addition

Offline Aznhmonglor

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Re: ButylLithium, THF, and H2O
« Reply #4 on: March 25, 2009, 10:34:28 PM »
Please do that would be a big help.

Offline wanderlust

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Re: ButylLithium, THF, and H2O
« Reply #5 on: March 25, 2009, 10:38:52 PM »
Sorry I modified my post if you reread my last post there's a wikipedia link there that should be very useful for you.

Offline Aznhmonglor

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Re: ButylLithium, THF, and H2O
« Reply #6 on: March 25, 2009, 10:40:26 PM »
Thank you it makes sense now. But for some reason in my notes it says that with a conjugated compound the strong basic nucleophile still attacks the carbonyl group and forms an alcohol?

Offline wanderlust

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Re: ButylLithium, THF, and H2O
« Reply #7 on: March 25, 2009, 11:06:31 PM »
With a alpha beta unsaturated carbonyl I'm pretty sure the nucleophile attacks where I said.  Possibly double check your notes or ask your teacher for clarification. 

Offline Aznhmonglor

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Re: ButylLithium, THF, and H2O
« Reply #8 on: March 25, 2009, 11:29:43 PM »
Hmmm...this method didn't work....anybody got anymore ideas? I think it has to attack the carbonyl group?

Offline wanderlust

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Re: ButylLithium, THF, and H2O
« Reply #9 on: March 25, 2009, 11:37:07 PM »
Why didn't it work what was is the actual product then?

Offline Aznhmonglor

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Re: ButylLithium, THF, and H2O
« Reply #10 on: March 25, 2009, 11:49:03 PM »
Im not sure but it didn't come out correct if you attack the alkene and let the carbonyl group stay.

Offline wanderlust

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Re: ButylLithium, THF, and H2O
« Reply #11 on: March 26, 2009, 12:00:04 AM »


This product is showing as wrong? 

I don't know then.

Offline azmanam

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Re: ButylLithium, THF, and H2O
« Reply #12 on: March 26, 2009, 06:37:30 AM »
alkyl lithiums are hard nucleophiles and therefore give the 1,2 add'n product.  tertiary alcohol is the correct answer.  Gillman reagents (alkyl cuprates) are the ones that give 1,4 conjugate add'n.
Knowing why you got a question wrong is better than knowing that you got a question right.

Offline sjb

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Re: ButylLithium, THF, and H2O
« Reply #13 on: March 26, 2009, 07:22:15 AM »

(picture of 3-butylcyclohexanone)

This product is showing as wrong? 

I don't know then.

Also don't forget to count your carbons :)

Offline Aznhmonglor

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Re: ButylLithium, THF, and H2O
« Reply #14 on: March 26, 2009, 09:23:17 AM »
So this would be correct answer?


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