OCR Chemistry - Benzene

A quick mindmap to outline kekules and the modern day structure of benzene, and why it is that, and the reactions of benzene and some uses of the benzene compounds made in the reactions.

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  • Benzene
    • Reactions
      • Nitration
        • Electrophilic Substitution
        • Conc. Sulphuric (catalyst) and conc. nitric acid.
        • Temp of 50 degrees celcius
        • Uses of Nitrobenzene
          • Dyes
          • Pharmaceuticals
      • Halogenation
        • Requires a halogen carrier. e.g. FeCl3, AlBr3.
        • Electrophilic substitution
        • Halogen reacts with benzene at RTP with the appropriate halogen carrier.
        • Uses
          • Bromobenzene
            • In the preparation of pharmaceuticals
  • Structure
    • Benzene
      • Reactions
        • Nitration
          • Electrophilic Substitution
          • Conc. Sulphuric (catalyst) and conc. nitric acid.
          • Temp of 50 degrees celcius
          • Uses of Nitrobenzene
            • Dyes
            • Pharmaceuticals
        • Halogenation
          • Requires a halogen carrier. e.g. FeCl3, AlBr3.
          • Electrophilic substitution
          • Halogen reacts with benzene at RTP with the appropriate halogen carrier.
          • Uses
            • Bromobenzene
              • In the preparation of pharmaceuticals
    • Kekule thought there were 3 C=C bonds - could be a resonance hybrid between 2 forms, bonds must move.
    • C6H6
  • Modern structure - The delocalised model. (& why Kekule was wrong)
    • Structure
      • Kekule thought there were 3 C=C bonds - could be a resonance hybrid between 2 forms, bonds must move.
      • C6H6
    • C-C bonds are the same length
    • Low reactivity due to ring of delocalised electrons
    • Lower enthalpy of hydrogenation than expected (3x the energy for 1 double bond).
  • Failed to explain the low reactivity
    • Would be expected to undergo addition reactions, e.g. reaction with bromine water, decolourising it. Does not happen.
      • P electrons are spread over all 6 Carbon atoms. Creates a ring of electron density above & below plane of carbon atoms
        • Modern structure - The delocalised model. (& why Kekule was wrong)
          • C-C bonds are the same length
          • Low reactivity due to ring of delocalised electrons
          • Lower enthalpy of hydrogenation than expected (3x the energy for 1 double bond).
      • Benzene has no E/Z isomers like some alkenes would.
        • Chlorobenzene
          • As a solvent
          • Int eh production of pesticides

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