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Topic: please check my simple E2 reaction  (Read 5033 times)

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Offline iScience

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please check my simple E2 reaction
« on: January 20, 2014, 12:43:19 AM »
http://i.imgur.com/mk8eGes.png

(the base i'm adding is potassium tert-butoxide and the solvent is tert-butanol)

i'm under the assumption that the radicals don't rearrange (is this correct?) and that the cationic center is what moves around

Offline iScience

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Re: please check my simple E2 reaction
« Reply #1 on: January 20, 2014, 12:45:47 AM »
so basically the double bond forms at the location of nucleophilic attack right?

Offline discodermolide

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Re: please check my simple E2 reaction
« Reply #2 on: January 20, 2014, 12:46:32 AM »
How do you form cations in the presence of base?
The product is ok, but the mechanism not. It is an elimination reaction.
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Offline iScience

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Re: please check my simple E2 reaction
« Reply #3 on: January 20, 2014, 01:46:52 AM »
if i didn't have the cation how would i form a double bond?

would it be more appropriate if i stated that the basic solution was very dilute?

Offline discodermolide

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Re: please check my simple E2 reaction
« Reply #4 on: January 20, 2014, 01:53:22 AM »
It is an elimination reaction, what is eliminated to form the double bond?
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Offline iScience

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Re: please check my simple E2 reaction
« Reply #5 on: January 20, 2014, 02:44:42 AM »
the bromine

Offline discodermolide

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Re: please check my simple E2 reaction
« Reply #6 on: January 20, 2014, 02:48:07 AM »
Yes, and what else is eliminated?
What is the difference between the starting material and the product, which elements are in the starting material but not in the product?
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Offline iScience

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Re: please check my simple E2 reaction
« Reply #7 on: January 20, 2014, 02:49:40 AM »
one bromine and one hydrogen are eliminated: i don't yet see where this is going

Offline discodermolide

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Re: please check my simple E2 reaction
« Reply #8 on: January 20, 2014, 03:56:57 AM »
The base abstracts a proton which results in the elimination of Br- giving a double bond.
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Offline AlphaScent

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Re: please check my simple E2 reaction
« Reply #9 on: January 20, 2014, 10:15:49 AM »
You mention an E2 mechanism.  Do you know the properties of an E2 elimination??  Disco in his drawing above is demonstrating one of those properties.  Could you tell me what that property is?
If you're not part of the solution, then you're part of the precipitate

Offline iScience

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Re: please check my simple E2 reaction
« Reply #10 on: January 20, 2014, 11:46:12 AM »
the property is that stuff gets eliminated right?

the reaction i'm wondering about is that when the tbut-O- attacks a non-adjacent carbon, not a n adjacent one.

i was curious how the mechanism would proceed then...

even for the mechanism you drew, you still form a cation when the bromine leaves which then forms the pi bond is this not correct?..

can you guys just tell me the answer kind of pressed for time.

thanks guys

Offline iScience

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Re: please check my simple E2 reaction
« Reply #11 on: January 20, 2014, 12:42:41 PM »
for E2 reactions, do the alpha and beta carbon have to be adjacent? If so, why can the cationic center not propogate to the location of the lone pairs as i have drawn in my picture?

Offline discodermolide

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Re: please check my simple E2 reaction
« Reply #12 on: January 20, 2014, 01:53:35 PM »
the property is that stuff gets eliminated right?

the reaction i'm wondering about is that when the tbut-O- attacks a non-adjacent carbon, not a n adjacent one.

i was curious how the mechanism would proceed then...

even for the mechanism you drew, you still form a cation when the bromine leaves which then forms the pi bond is this not correct?..

can you guys just tell me the answer kind of pressed for time.

thanks guys


The is NO cation formed, the reaction is concerted, the H is abstracted and the negative charge moves in to form the pi bond and causes the bromine to leave. The H that is abstracted must be trans and antiperiplanar to the leaving group.
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Offline AlphaScent

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Re: please check my simple E2 reaction
« Reply #13 on: January 20, 2014, 03:59:35 PM »
"stuff gets eliminated"

Go read about E2 mechanisms before coming here to waste our time. 

Don't miss your lectures and expect us to spoon feed you answers.
If you're not part of the solution, then you're part of the precipitate

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