Electrophilic substitution reactions of benzene

Question 1

What occurs during the nitration of benzene?

Answer 1

• Benzene reacts slowly with nitric acid with a sulfuric acid catalyst and heated to 50 degrees
• A hydrogen atom is then replaced by a nitro -NO2 group
• This requires concentrated nitric acid and concentrated sulfuric acid

Question 2

What are the steps of the mechanism of the nitration of benzene?

Answer 2

1. HNO3 + H2SO4 = No2+ + HSo4 + H20
2. mechanism x
3. H+ + Hso4- = H2SO4

Question 4

Why is benzene more resistant to electrophilic substitution than alkenes?

Answer 4

• In benzene, there are delocalised electrons and the pi bonds are all delocalised, overlapping over the ring
• However, in alkenes, the electrons are localised
• This means alkenes have a higher electron density than benzene
• therefore, alkenes can polarise chlorine/bromine/nitrogen more than benzene and are less resistant than benzene which requires a halogen carrier