Nitration

Question 1

Why does benzene undergo substitution rather than addition reactions?

Answer 1

Benzene resists addition reactions because that would involve breaking the delocalisation and losing that stability. Substitution reactions only temporarily breaks it and delocalisation of the p electrons is maintained.

Question 2

How is the nitronium ion produced and balanced equation?

Answer 2

By reacting concentrated sulphuric and nitric acid.

2H2SO4 + HNO3 –> NO2(+) + H3O(+) + 2HSO4-

Question 3

How is H2SO4 regenerated in the nitration of benzene?

Answer 3

HSO4(-) + H+ –> H2SO4 (H+ from benzene ring).

Question 4

How do you prepare an aromatic amine?

Answer 4

The NO2 group of nitrobenzene is usually reduced to the NH2 group. A tin catalyst is used and concentrated hydrochloric acid is the reducing agent (this would usually form the ammonium salt so NaOH is added to give the amine.

Question 5

Which mechanism shows nitration of benzene?

Answer 5

Electrophilic substitution (electrophiles attracted to delocalised electrons)