Aromatics A2

Question 1

Describe the shape of benzene

Answer 1

Flat, hexagonal with delocalised electrons in the middle. Each bond is equal in length

Question 2

How is the electron circle formed in benzene

Answer 2

P-orbitals from each carbon overlap and cause the electrons in each orbital to delocalise

Question 3

What is the Kekule shape

Answer 3

Cyclohexane with 3 double bonds

Question 4

What is the thermochemical evidence to disprove Kekule and prove aromatic stability

Answer 4

To hydrogenate Kekule, has an enthalpy of -360. But benzene has an enthalpy of -208. Therefore, this is more stable

Question 5

Compare benzene’s boiling point to hexane

Answer 5

Higher boiling point as the flat shape allows it to be tightly packed

Question 6

What is benzene attacked by

Answer 6

Electrophiles

Question 7

Describe the mechanism of electrophilic substitution

Answer 7

Electrophile takes electron from benzene, benzene then loses an hydrogen to become neutral again

Question 8

What is nitration

Answer 8

Substituting NO2 for any hydrogen in benzene

Question 9

How is the electrophile for nitration formed

Answer 9

H2SO4 + HNO3 -> NO2+ + HSO4- + H2O

Question 10

What are uses of nitrobenzenes

Answer 10

Explosives, industrial dyes

Question 11

How is the electrophile formed for Friedel-Crafts acylation

Answer 11

RCOCl + AlCl3 -> RCO+ + AlCl4-

Question 12

What is the catalyst for Friedel-Crafts acylation

Answer 12

AlCl3 as it’s formed again after the reaction