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Topic: Substitution or elimination?  (Read 1901 times)

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Offline dodopa

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Substitution or elimination?
« on: March 18, 2018, 03:27:25 PM »
Hello,

I want to ask you for product in this reaction. Substrate is 2° so when I add t-BuOK, I think, it will be E2 by Hofmann rule. But what happens when I have CH3ONa, it should be also E2 by Zaitsev rule, but in antiperiplanar position is methyl not H, so what will be main product? It will be same asi with t-BuOK or it will by substitution or this reaction doesn´t work?


Thanks for *delete me* :-)

Offline pgk

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Re: Substitution or elimination?
« Reply #1 on: March 20, 2018, 12:40:33 PM »
Under basic conditions and apart few extreme exceptions:
1). Primary substrates prefer SN2 substitution than E2 elimination; but E2 elimination can sometimes occur, when a strong/hard base has to attack to a poor leaving group.
2). Secondary substrates prefer E2 elimination than SN2 substitution; but SN2 substitution can also occur (but not exclusively), when a strong/hard base has to attack to a good leaving group, especially when the leaving group is a hard to borderline or a borderline base.
3). Tertiary substrates prefer E2 elimination.
4). E2 elimination prefers the Zaitsev rule, except in case of a steric hindered base or lack of the appropriate hydrogen that follows the Hoffmann rule.
Now, can you give the answer to your question, by yourself?
« Last Edit: March 20, 2018, 01:36:01 PM by pgk »

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