Road Map 3 Destroyer

[Mamona]

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I need your help to understand this Road map. If you start and go to the right we have an addition of Br to the ring. Going up from there a E2 rxn happens, and the double bond goes up. From the same ring with Br going down, I am having troble identifing if there is a E2 or E1 (I think is E1, we have a polar protic solvent and Br is in 3 position??). Now my other question, if you start and go to the left the ring also add a Br going down heat, Alc and KOH, will make a E2, why the double bond goes in a different direction from the other E2 rxn.

Thank you in advance

 

[tranv117]

E1: acid and high temp, also like SN1 prefers tertiary>secondary>primary
E2: base and high temp, like SN2 prefers primary>secondary>tertiary, also...E2 must have H anti to the leaving group

 

[Mamona]

E1: acid and high temp, also like SN1 prefers tertiary>secondary>primary
E2: base and high temp, like SN2 prefers primary>secondary>tertiary

Thanks trav117, but it is C2H5O-K+ / C2H5OH and E1, or E2. Why the different ways of making a double bond????

 

[tranv117]

I briefly explained this in another thread. When doing elimination reactions, it depends on the base. One is a very bulky base while the other is not. with a bulky base, which is easier for the base to pull off the H? The H on the ring or the H on the open methyl group? Methyl group is more in the open space so it is easier to pull that off.

Look up Zaitsev vs Hoffman eliminations.

With Zaitsev, you prefer to form the most stable alkene (ie. most substituted) but when you have a big bulky base, preference goes to the less substituted alkene.

 

[Mamona]

I briefly explained this in another thread. When doing elimination reactions, it depends on the base. One is a very bulky base while the other is not. with a bulky base, which is easier for the base to pull off the H? The H on the ring or the H on the open methyl group? Methyl group is more in the open space so it is easier to pull that off.

Look up Zaitsev vs Hoffman eliminations.

With Zaitsev, you prefer to form the most stable alkene (ie. most substituted) but when you have a big bulky base, preference goes to the less substituted alkene.

Thank you very much for your answer now I understand the difference!!!