Aromatic Chemistry

• Who is the presenter of the aromatic chemistry video?

  Chris Harris
• What exam board is the video dedicated to?

  AQA
• What is the molecular formula of benzene?

  C₆H₆
• What type of structure does benzene have?

  Cyclic and planar
• How many valence electrons does each carbon in benzene have?

  Four valence electrons
• What is the bond length of carbon-carbon bonds in benzene?

  139 picometers
• What does the delocalized electron structure of benzene contribute to?

  Stability and equal bond lengths
• What is the name of the structure that represents benzene with alternating single and double bonds?

  Kekulé structure
• What does the circle in the skeletal formula of benzene represent?

  Delocalized electrons
• Why is benzene more stable than cyclohexene?

  Due to its delocalized electron structure
• How do you measure the stability of benzene?

  By comparing enthalpy changes of hydrogenation
• What is the enthalpy change of hydrogenation for cyclohexene?

  -120 kilojoules per mole
• What is the predicted enthalpy change of hydrogenation for benzene if it had three double bonds?

  -360 kilojoules per mole
• What is the actual enthalpy change of hydrogenation for benzene?

  -208 kilojoules per mole
• What does a lower negative enthalpy change indicate about benzene's stability?

  More energy is required to break its bonds
• What is an arene?

  An aromatic compound containing benzene
• What is phenol?

  Benzene with a hydroxy group (OH)
• What type of reaction do arenes undergo?

  Electrophilic substitution
• What are the two types of electrophilic substitution reactions mentioned?

  Friedel-Crafts and nitration
• Why do benzene rings resist addition reactions?

  To maintain their stable delocalized structure
• What happens to the hydrogen atom during electrophilic substitution in benzene?

  It is replaced by an electrophile
• What is the significance of the hydrogen atoms in the skeletal formula of benzene?

  They are implied but not shown
• Who are the chemists associated with Friedel-Crafts reactions?

  Friedel and Crafts
• What are the key properties of benzene?

  • Cyclic and planar structure
  • Molecular formula C₆H₆
  • Delocalized electron structure
  • Equal bond lengths of 139 picometers
  • Stable compared to cyclohexene
• What are the steps to demonstrate benzene's stability?

  1. Compare enthalpy changes of hydrogenation.
  2. Measure enthalpy change for cyclohexene (-120 kJ/mol).
  3. Predict enthalpy change for benzene with three double bonds (-360 kJ/mol).
  4. Measure actual enthalpy change for benzene (-208 kJ/mol).
  5. Conclude that benzene is more stable due to delocalized electrons.
• What are the naming conventions for derivatives of benzene?

  • Add "benzene" at the end (e.g., bromobenzene).
  • Use "phenol" for benzene with an OH group.
  • Use "phenyl" for amine derivatives (e.g., phenylamine).
• What are the mechanisms of electrophilic substitution in benzene?

  • Electrophilic substitution replaces hydrogen with an electrophile.
  • Two main reactions: Friedel-Crafts and nitration.
  • Benzene's stability prevents addition reactions.
• What type of reaction do benzene undergoes due to its stability?

  Electrophilic substitution
• Why is benzene difficult to react with?

  Its stable structure hinders reactivity
• What are the two types of electrophilic substitution reactions for benzene that need to be known?

  • Friedel-Crafts acylation
  • Nitration reaction
• Who are the scientists after whom Friedel-Crafts acylation is named?

  Charles Friedel and James Kraft
• Why is benzene important in pharmaceuticals?

  It is essential for drug synthesis
• What does the Friedel-Crafts acylation reaction involve?

  Adding an acyl group to benzene
• What is the role of acyl chlorides in Friedel-Crafts acylation?

  They provide the acyl group for substitution
• What is required to make the acyl chloride reactive enough for benzene?

  A halogen carrier like AlCl3
• What does the halogen carrier do in Friedel-Crafts acylation?

  It creates a stronger electrophile
• What is formed when the acyl chloride reacts with the halogen carrier?

  A powerful carbocation electrophile
• What happens to the delocalized electrons in benzene during Friedel-Crafts acylation?

  They are attracted to the electrophile
• What is the product of the Friedel-Crafts acylation reaction?

  A phenyl ketone
• What is the significance of the hydrogen in the benzene ring during the reaction?

  It is replaced by the acyl group