5 - Substitution Reactions Of Benzene

Question 0

In electrophilic substitution what happens to the delocalised electron ring?

Answer 0

Ring is disrupted when intermediate forms, then H+ ion comes off, and stability is resumed by restoring the ring with the new substituted atom.

Question 1

How does electrophilic substitution occur?

Answer 1

Electrophilic accepts a pair of electrons from delocalised electron ring. These are Pi electrons. An intermediate forms with both hydrogen atoms and the atom being substituted. This disrupts the delocalised electron cloud. It loses a H+ as it unstable. Ring ere forms to become stable.

Question 2

What does Sulphuric acid do in the nitration of benzene?

Answer 2

Sulphuric acid generates an electrophilic from nitric acid. The generated electrophilic is the nitryl cation (NO2+). HNO3 + H2SO4 -> NO2+ + H2SO4- + H2O.

Question 3

What is the electrophilic that is generated?

Answer 3

Nitryl cation - NO2+.

Question 4

What does benzene react in the presence of? What is this reaction?

Answer 4

Benzene reacts in the presence of a halogen carrier. Br+ is more electrophilic than Br2. Br2 + FeBr3 -> Br- + FeBr4- - the left over H+ that’s been substituted off can now react with FeBr4- to form FeBr3 + HBr.

Question 5

What may be the halogen carriers?

Answer 5

AlX3 or FeX3.