E1 using KOt-Bu

[Emmyg1979]

On a recent exam I was asked to identify the mechanism when 1-bromo-1-methylcyclohexane was reacted with KOt-Bu in HOt-bu, no other conditions were given (temp, concentration, etc).  

I inferred the lack of conditions to imply equal amounts of base and solvent at room temperature; I said E2; this was wrong.  My professor explained that because the base was so bulky, the substrate was both tertiary and bulky, and the solvent was protic, a C+ would form before the base could "get" over to the substrate and this would proceed through an E1 mechanism.

I am having a difficult time understanding this explanation because it is my understanding that the conjugate acid of a strong base is often used as the solvent, that strong bulky bases will proceed through E2 (Hoffman) mechanism given a 1°, 2°, or 3° substrate, with 3° being the best (unless the substrate is a benzene or allylic which prefer E1).

I have found many examples using the same substrate and base, but without a solvent listed; they are all E2.  I have found several references stating that sterics do not effect basicity.   I have also found many examples of bulky 3° alkyl bromides, that are not 1-bromo-1-methylcyclohexane, reacting with KOt-Bu in HOt-Bu which proceed via E2.

Can anyone explain this and/or outline some guidelines for differentiating between E1 and E2 given similar scenarios?

[Emmyg1979]

I am reposting this because it was marked as answered, but has not been.

Any response would be greatly appreciated!

Thank you.

[Emmyg1979]

Ok... I’ll try to start this conversation by acknowledging that up to this point I have had 2 chemists & 2 different tutors explain that this reaction would likely proceed through E2 unless the concentration of the KOt-Bu was very low, or the temperature was high.

I am asking here to try and verify because I will be taking the ACS exam soon, and after that the PCAT &/or MCAT (who’s resources are where I found this substrate & base, without the solvent, proceeding via E2).

I both like and respect my professor, who has excellent credentials and experience.  I don’t think he is mistaken, but if he is it’s just that, a mistake.  I am not asking to dispute him, it is simply very important that I understand this for my own long term goals and successes.