3.3.10.1 bonding

• what is benzene?


  aromatic compound with a ring of 6 carbon atoms with 6 hydrogen atoms and a ring of delocalised electrons

  
• length of bonds


  each bond in the benzene ring has an intermediate length in between a double and a single bond
• electron structure


  outer electron from the p-orbital of each carbon is delocalised to form the central ring
• ring structure 


  makes benzene very stable compared to other molecules of a similar size
• cyclohexatriene vs benzene

  • when Benzene was first discovered, its structure wasn't known
  • predicted from empirical measurements that it has a similar structure to cyclohexatriene

  
• prediction of enthalpy change of hydrogenation for benzene

  -360 kJmol-1
• actual enthalpy change of hydrogenation of benzene

  -208 kJmol-1
• arenes


  compounds that contain benzene as part of their structure
• arenas physical properties

  high melting points due to high stability of the delocalised ring but low boiling points as they are non-polar molecules and often cannot be dissolved in water