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Topic: What is SNi'?  (Read 12807 times)

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Offline Hikaru

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What is SNi'?
« on: July 29, 2008, 12:03:29 PM »
SNi is intramolecular substitution reaction.
How is it different from SNi'?

Offline azmanam

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Re: What is SNi'?
« Reply #1 on: July 29, 2008, 12:25:18 PM »
' usually refers to allylic substitution.  in general:

H2C=CH-CH2-LG  +  Nuc:  -->  Nuc-CH2-CH=CH2

where the nucleophile attacks the carbon of the double bond, the electrons move to form a new double bond on the adjacent carbon, and the leaving group leaves.

This might be what it refers to here.
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Offline Mitch

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Re: What is SNi'?
« Reply #2 on: July 29, 2008, 03:21:06 PM »
I think this has more to do with nucleophillic substitution that occurs within a molecule with itself.
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Offline macman104

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Re: What is SNi'?
« Reply #3 on: July 29, 2008, 03:46:31 PM »
I think this has more to do with nucleophillic substitution that occurs within a molecule with itself.
But if SNi is already intramolecular, then what designation would the ' have?

Offline azmanam

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Re: What is SNi'?
« Reply #4 on: July 30, 2008, 07:52:12 AM »
Here's the SNi wikipedia page.

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

Seems more like substitution resulting from tight ion pair, thus proceeding with retention.  So maybe this general mechanism, but with allylic substitution?
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Offline Hikaru

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Re: What is SNi'?
« Reply #5 on: July 31, 2008, 12:35:33 AM »
Thanks a lot.
I think it is like azmanam said - that it is allylic substitution.
Can it be both allylic substitution and intermolecular?

Actually this question comes from a problem:
Which one reacts with SOCl2the fastest?
Ph-CH2OH 
CH2=CHCH2OH
CH3CH=CHOH
CH3CH2CH2OH
I am told they occur through SNi' mechanisms.

Offline azmanam

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Re: What is SNi'?
« Reply #6 on: July 31, 2008, 07:48:44 AM »
careful with your prefixes.  SN2' reactions are the intermolecular ones.  The whole point here is that we're dealing with SNi' reactions, which are intramolecular.

Let's assume that SNi' refers to intramolecular allylic substitution.  Which compound appears capable of allylic substitution under this mechanism?  What is the mechanism for this SNi' reaction?
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Offline azmanam

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Re: What is SNi'?
« Reply #7 on: August 14, 2008, 01:58:26 PM »
Better late than never, right?

Here's a page talking specifically about SNi' that actually refers to one of the choices in the multiple choice question:

http://www.cem.msu.edu/~reusch/VirtTxtJml/special2.htm#top6
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