E2/E1 rxn confusion

[ekam]

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When 2-chloro butane reacts with (CH3)3CO- K+ / (CH3)3COH
it gives but-1-ene

My questions?
Is (CH3)3CO- K+ strong base ?
If yes, and this is E2 rxn, then why doesn't it give but-2-ene?
According to CHad, LG takes hydrogen from more substituted carbon

Help me Please!!

 

[ThunderSplash]

I was stuck on this earlier and after some research, I think it's because the base is so bulky and the terminal hydrogens are the easiest to access. That's why you get a Hoffman product instead of Zeitsev.

 

[ekam]

Makes sense. I think I need to review my notes again. Thank you!

 

[DAT Destroyer]

When 2-chloro butane reacts with (CH3)3CO- K+ / (CH3)3COH
it gives but-1-ene

My questions?
Is (CH3)3CO- K+ strong base ?
If yes, and this is E2 rxn, then why doesn't it give but-2-ene?
According to CHad, LG takes hydrogen from more substituted carbon

Help me Please!!

This reagent is potassium tert-butoxide. It is a strong base , but a poor nucleophile due to its steric bulk. This reagent does indeed give the E2 product of 1-butene in about 95% yield. The 2-butene would also form....perhaps 5% if you are lucky. I am sure one of the texts,,,,,,Jones, Bruice, Klein, Claden could give you EXACT number % if they did the experiment, but it would be close to what I estimate. This strong base would have much difficulty in abstracting the inner proton. The outer proton is much easier. This is exactly what we find. If we made the base even LARGER,,,,,,perhaps put 3 ethyl groups on the reagent base.....we could likely see 98% 1-butene,,,,,perhaps more !

Hope this helps.

Dr. Jim Romano

 

[ekam]

Thank you Dr Jim, your book is a great resource!! Thank you for clarification!!