E1 vs E2

Question 1

What determines whether an elimination reaction will proceed via E1 or E2?

Answer 1

The strength of the base

Question 2

Which mechanism (E1 or E2) requires a strong base?

Answer 2

E2

Question 3

Which mechanism does not require a strong base to proceed? Why?

Answer 3

E1. Because carbocation intermediate formed independent of base (this is the slow step)

Question 4

What species/base is most likely to remove the H+ to form the double bond?

Answer 4

H2O (because most abundant base in aq solutions)

Question 5

Are E1 reactions most likely to occur on primary, secondary or tertiary C?

Answer 5

Tertiary (as methyl groups help to stabilise carbocation intermediate)

Question 6

What type of reactions are E1 reactions likely to cooccur with?

Answer 6

SN1 (same intermediate)

Question 7

What is the rate determining step in an E2 reaction?

Answer 7

The only step (all bonds broken/formed at same time)

Question 8

Are E2 reactions most likely to occur on primary, secondary or tertiary C? Is this the same or different to SN2?

Answer 8

Any/all.

This differs to SN2 because proton is removed from opposite side, bulk around C-X doesn’t affect