Colour by design

Question 1

What is the molecular formula of benzene

Answer 1

C6H6

Question 2

What is the Kekulé structure of benzene

Answer 2

Alternating single and double bonds that continuously flip between carbons

Question 3

What is the delocalised model of benzene?

Answer 3

Each carbon donates an electron from its p-orbital which all combine to form a ring of delocalised electrons

Question 4

What are the three pieces of evidence that support the delocalised model of benzene?

Answer 4

1. X-ray diffraction shows that all the c-c bonds are the same length
2. Bromine water and benzene do not react (no colour change) but bromine and alkene do not react. You would expect electrophilic addition to occur if benzene had a kekulé structure
3. The enthalpy change of cyclehexene is -120kj/mol but benzene is -208k/mol (less than 3 x-120) so more energy must have been put into the bonds in benzene than if it were the kekulé structure.

Question 5

What is an arene

Answer 5

A group with a benzene ring

Question 6

Benzene + Nitronium ion

Conditions needed

Answer 6

Electrophilic substitution: Nitrobenzene
**

Warm with H2SO4 + HNO3

If you only want one NO2 group then you must keep temperatures under 55C

Question 7

Benzene and Sulfur trioxide

Answer 7

Electophilic addition: Benzenesulfonic acid