Electrophilic Aromatic Substitution

Question 1

What are the steps in EAS?

Answer 1

electrophilic addition step
- slow rate determining step
= adds the electrophile to the aromatic ring

elimination of the proton
- fast step

Question 2

How do R substituents affect EAS?

Answer 2

the first R substituent attached affects the position of the second R substituent added

Question 3

What are the two types of R substituent?

Answer 3

activating
- further EAS occurs
- makes the ring more reactive
= makes the ring more electron rich than benzene by donating electrons

deactivating
- less EAS occurs
- makes the ring less reactive
= makes the ring less electron rich than benzene by withdrawing electrons

Question 4

What are the methods of donating and withdrawing electrons from the aromatic ring?

Answer 4

inductive
- effects bond polarity via the sigma bonds

resonance
- occurs via the pi bond
= p-orbital overlaps with pi orbitals creating further delocalisation which increases EAS

Question 5

What are the inductive groups?

Answer 5

donating
- alkyl groups = CH3

withdrawing

• halogens = Cl, Br, F
• cyano = CN
• nitro = NO2

Question 6

What are the deactivating groups?

Answer 6

ortho/para, inductive
- halogens = Cl, Br, F

meta, inductive

• cyano = CN
• nitro = NO2

meta, resonance

• carboxylic acid = COOH
• COCH3
• CHO

Question 7

What are the activating groups?

Answer 7

inductive
- alkyl groups = CH3

resonance

• OCH3
• NH2
• Ph
• OH
• NHCOCH3