A2 AQA CHEM4 3.4.6

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  • Created by: Nuha
  • Created on: 23-04-14 12:51

3.4.6 Aromatic Chemistry


·         C6H6 with delocalised electrons above and below the plane (one of the p-orbital electrons for each carbon is not involved in bonding since carbon bonds with 1 hydrogen

·         Planar structureà All bond angles are 120o (trigonal planar)

·         Bond lengths are identical. The actual length is in between the length of C-C and C=C (intermediate length)

Delocalisation stability

·         Benzene is more stable than cyclohexatriene (hypothetical)

·         Hypothetical  ΔH would be -360KJmol-1 but the ΔH of benzene is -208KJmol-1 which means it is 152KJmol-1 less exothermic and therefore more stable

·         This stability is caused by the delocalised electrons (hence the difference of 152 is the delocalisation enthalpy)

Electrophilic substitution

·         Electrophilic attack in arenes (containing one or more benzene rings) results in substitution of one of the hydrogens…therefore a H+ will be eliminated

·         Delocalised electrons in benzene ring act as area…


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