E1 or E2

[Zayan]

I had this question

Screenshot_2024-09-01-12-59-00-87_6012fa4d4ddec268fc5c7112cbb265e7.jpg

I did it by E₂ mechanism since it's tbuoh (bulky base) and made the hoffman product so option A.
But the solution manual did it by E₁ and did rearrangement to get option C.
What is the correct mechanism of this reaction and hence the correct major product?

[ChenBeier]

I would say some percentage b and also c.

The iodine will be eliminated. A positive charge will remain on this carbon. But this is instable, a H hydrogen from next C-atom with methylgroup will jump in and the charge will go to the next or over the next C- atom, because the methyl or ethylgroups stabilise the carbenium. One of them will loose a hydrogen and the double bond will be formed.

[Zayan]

But why did you do the E₁ mechanism. It's tert butyl alcohol(bulky base) shouldn't it do the hoffman E₂ elimination making option A?

[ChenBeier]

It's tert butyl alcohol. It's only solvent not a base. We don't talking about potassium tert butylate. The Elimination is only done by heat as also written.

[Zayan]

Can you please list a strong bases and weak bases so that I can differentiate between E₁ and E₂ I often get stuck is there a way to know what to prefer

[ChenBeier]

Strong, alcoholates R-O- Me+, Hydroxide MeOH, Me(OH)₂ Me = Alcali- and earth alcali metall
weak Ammonia, alkylamines, Arylamines , water , Alcohol,

A strong base is a base that is 100% ionized in solution. If it is less than 100% ionized in solution, it is a weak base.

Check list of pKb values