Benzene

• Molecular formula of benzene

  C6H6
• Disproving Kekule's model


  The enthalpy change of hydrogenation is less exothermic than expected. (the negative value is too low)
• Disproving Kekule's model


  Bond lengths in benzene are all the same length and are intermediate between carbon double bonds and carbon single bonds
• Disproving Kekule's model


  Benzene has low reactivity and does not undergo electrophilic addition reactions
• Describing the structure of benzene


  -Beneze is a planar molecule.

  -Beneze's adjacent P orbitals overlap sideways.

  -Forms a Pi system above and below the molecule.

  -Electrons are delocalised around the ring.

  -Carbon to Carbon bonds are all the same length.
• Electrophilic reactions of benzene

  Nitration of benzene.

  Halogenation of benzene.

  Alkylation of benzene.
• Nitration of benzene


  condition: H2SO4 (concentrated sulfuric acid as a catalyst).

  condition: HNO3 (concentrated nitric acid forms nitronium ion)

  Tempreature: The higher the temp, the more substitution takes place
• Halogenation of benzene


  condition: Halogen carrier catalyst (AlX3)
• Alkylation of benzene


  conditon: haloalkane in the presence of benzene

  condition: halogen carrier catalyst (AlX3)