Directing groups

Question 1

What is an example of a deactivating group?

Answer 1

• NO2
• Deactivates the aromatic ring and reacts less readily with electrophiles - bromine is a good example
• Therefore requires higher temp. to speed rate of reaction and a halogen carrier catalyst
• ‘Directs’ second substituent to position 3 (meta)
• Is less susceptible to ESR than benzene itself!!

Question 2

What is an example of an activating group?

Answer 2

• NH2
• Activates aromatic ring and reacts more readily with electrophiles, bromonium is a good example.
• Does not need increased temp. or halogen carrier catalyst
• ‘Directs’ second substituent to positions 2/4 (ortho/para)

Question 3

What are the set rules concerning directing groups?

Answer 3

• ALL 2/4 (ortho/para) directing groups are ‘activating’ groups.
• ALL 3(meta) directing groups are ‘deactivating’ groups.

Question 4

What is the second substitution called?

Answer 4

Disubstitution

Question 5

What other factor can affect proportions of different substituted isomers?

Answer 5

• A large substituted isomer can get in the way.

- It’s also known as ‘the steric effect’.