destroyer orgo #80

[Tina324]

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Hey guys I have yet another q =)

There is one part to the q that I don't understand. According to the solutions:
2-chlorobutane reacts with (CH3)3CO- K+ to yield 1-butene

If this is an E1 (hmm or E2..which one? lol) reaction..shouldn't the most substitued alkene be formed?? i.e. 3 butene?

what are ur thoughts??

 

[ldm0208]

Hey guys I have yet another q =)

There is one part to the q that I don't understand. According to the solutions:
2-chlorobutane reacts with (CH3)3CO- K+ to yield 1-butene

If this is an E1 (hmm or E2..which one? lol) reaction..shouldn't the most substitued alkene be formed?? i.e. 3 butene?

what are ur thoughts??

because the strong base is bulky tertiary, so due to the steric hind, it must do "outside elimination" thereby forming the less substituted alkene!!

 

[DRHOYA]

The base is HUGE, so it would be E2 in this case. And again, since the base is HUGE, there are steric forces involved, it takes from the least substituted carbon. It is called the "Hoffman Product". Hope that helps. Just think.....anything HUGE, or t-butoxide........E2.......Hoffman Product.

 

[harrygt]

It is an E2, not because the base is huge, but because we have a strong base. T-butoxide is the conjugate base of a weak acid, which is the same as being a strong base. Using a weak base like the alcohol itself would lead to an E1 mechanism.
Now, because the base is bulky, it detaches the most accessible Hydrogen [primary hydrogen], leading to 1-butene.