aromatic chemistry

• What type of compound is benzene?


  Aromatic compound
• How many carbon atoms are in a benzene molecule?


  Six carbon atoms
• How many hydrogen atoms are in a benzene molecule?


  Six hydrogen atoms
• What is unique about the bonds in the benzene ring?


  Each bond has an intermediate length between a double and single bond
• Why is benzene considered very stable compared to other molecules of similar size?


  Due to the delocalised electrons forming a central ring structure
• What was the predicted structure of benzene based on empirical measurements?


  A structure similar to cyclohexatriene
• What was the predicted enthalpy change of hydrogenation for benzene?


  • 360 kJ mol^-1
• What was the actual enthalpy change of hydrogenation for benzene?


  • 208 kJ mol^-1
• What conclusion can be drawn from the difference in predicted and actual enthalpy change of hydrogenation for benzene?


  Benzene has a different, unusual structure compared to cyclohexatriene
• What are compounds that contain benzene as part of their structure called?

  • Arenes
  • Aromatic compounds
• Why do arenes have high melting points?


  Due to the high stability of the delocalised ring
• Why do arenes have low boiling points?


  Because they are non-polar molecules
• What makes the delocalised ring in benzene susceptible to attack?


  It is an area of high electron density
• What is the process called when electrophiles attack the benzene ring?


  Electrophilic substitution
• What is the electrophile in the formation of nitrobenzene?


  The NO₂⁺ ion
• What is produced when concentrated sulfuric acid reacts with concentrated nitric acid?


  A reactive intermediate for the electrophile
• What happens when benzene is heated with the NO₂⁺ electrophile?


  The NO₂⁺ electrophile substitutes onto the benzene ring
• At what temperature does mono-substitution of the NO₂⁺ electrophile occur?


  55°C
• What is the consequence of temperatures greater than 55°C during the reaction with benzene?


  Multiple substitutions can occur
• What is Friedel-Crafts acylation?


  A reaction where the delocalised electron ring in benzene acts as a nucleophile
• What must be produced from the acyl chloride and aluminium chloride catalyst for Friedel-Crafts acylation to occur?


  A reactive intermediate
• What happens to the H⁺ ion removed from the benzene ring during Friedel-Crafts acylation?


  It reacts with the AlCl₄^- ion to reform aluminium chloride
• What is the product of Friedel-Crafts acylation?


  A phenylketone
• What is the benzene group referred to in the context of phenylketones?


  The phenyl group
• What are some common applications of phenylketones?

  • Industrial production of dyes
  • Pharmaceuticals
  • Explosives