Ochem question (regarding E reactions)

[lex1489]

---

Members don't see this ad.

I came across this question in Kaplan's online course:

I answered choice D because I assumed the carbocation would move over to the tertiary carbon. Why doesn't this happen?

Edit. Rereading the question/explanation I'm assuming it's because the reaction proceeds via E2, not E1? If the base were bulky it would proceed via E1, and the carbocation would have the opportunity to move, but since it is KOH and the rxn proceeds via E1, the double bond forms immediately after Cl elimination. Correct?

 

[Baylor2011]

E2 Reactions - Typical reagents Base/EtOH and heat. E2 reactions never make a carbocation intermediate. Whenever the base (nucleophile) plucks off the proton to make water, the electrons in that bond fall down and kick off the Chloride (Cl-)...therefore never making a carbocation intermediate, meaning no rearrangements

 

[RCT PC CRN]

E2 (which is you have here) - first order kinetics, single step, backside attack, no chance for rearrangement.

E1 - second order kinetics, two step, carbocation intermidiate, possible rearrangement.

Let say for instance you drive your reaction via E1, still you will not have rearrangement. Drop Cl out, form a carbocation, it's 2-carbocation..now look for neighboring carbon, can you move H or CH3 and see if you get anything better then secondary..I don't think in your case you will get anything bettter (i.e tertiary) so even though you do E1 (which is not the case) still you won't get rearrangement and you will ended up with same product as E2.