Benzene and aromatic compounds

Question 1

Describe kekulé model of Benzene.

Answer 1

a six membered ring of carbon atoms joined by alternating single and double bonds.

Question 2

Give three points disproving Kekulé’s model.

Answer 2

1. lack of reactivity of benzene: if there was a c=c double bond, it should decolonise bromine in an electrophilic addition reaction- this does not occur
2. the length of benzene c-c bonds are in-between that of a single and double bond
3. Hydrogenation enthalpies: if benzene had cyclohexa-1,3,5-triene, it should have a enthalpy change of hydration 3x of cyclohexene- not the case.
   The actual enthalpy change is less negative

Question 3

Nitration of Benzene

Answer 3

-HNO3/H2SO4 (NO2+)
-50’C
nitrobenzene

Question 4

Formation of phenylethanone: what name and type of reaction? and steps.

Answer 4

• Acylation reaction (electrophilic substitution)
• benzene+ ethanol chloride
• AlCl3
• forms phenylethanone and HCl

Question 5

Alkylation

Answer 5

• AlCl3 (the halogen carrier catalyst) and haloalkane