12. Elimination Reactions

Question 1

What is an elimination reaction?

Answer 1

The loos of an atom or group of atoms resulting in the formation of a multiple bond

Question 2

What is the difference between a base and a nucleophile?

Answer 2

• A base is a species with a lone pair that can accept a proton
• A nucleophile is a species with a (lone) pair of electrons that is attracted to an electron deficient species

Question 3

What is an E1 mechanism? First order elimination

Answer 3

The rate of reaction depends only on the concentration of the substrate

Rate = k x [R-X]

Question 4

What are the two steps of E1 mechanism?

Answer 4

• Step (a): ionisation which is SLOW

- Step (b): deprotonation which is fast

Question 5

What is the second order mechanism for elimination reactions?

Answer 5

• E2 mechanism
• The rate of reaction depends on both the concentration of the substrate and the base
• Rate = k x [R-X][Base]

Question 6

What happens when there is more than one product possible in an elimination reaction?

Answer 6

• Monosubstituted is the minor product
• E/Z isomers are the major products (most stable)

This is zaitsev’s rule