Aromatics

• What is the molecular formula of benze?

  C6H6
• How many valence electrons does each carbon atom in benzene have?

  Four valence electrons
• What type of orbital do the lone electrons of carbon in benzene occupy?

  P orbital
• What is the bond length of the carbon-carbon bonds in benzene?

  139 picometers
• How does the bond length in benzene compare to single and double bonds?

  It is between the lengths of single and double bonds
• What is the skeletal formula used for in organic chemistry?

  To simplify the representation of molecules
• Who is the chemist associated with the Kekulé structure of benzene?

  Auguste Kekule - chemist associated with the structure of benzene
• What does the circle in the benzene structure represent?

  Delocalized electrons
• What is the significance of hydrogen atoms in the skeletal formula of benzene?

  They are implied but not shown
• Why is benzene considered more stable than cyclohexene?

  Due to its delocalized electron structure
• 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 are the two types of reactions that benzene undergoes?

  Friedel-Crafts and nitration reactions
• What type of reaction do aromatic compounds undergo instead of addition reactions?

  Electrophilic substitution reactions
• Why do electrophilic substitution reactions occur in benzene?

  Due to the high density of electrons in the ring
• What is the name of the mechanism that benzene undergoes during reactions?

  Electrophilic substitution
• What happens to the hydrogen atom during electrophilic substitution in benzene?

  It is replaced by an electrophile
• What are the derivatives of benzene and how are they named?

  • Derivatives include halogenated compounds, methyl groups, and nitro groups.
  • Named by adding the group to the end of "benzene" (e.g., bromobenzene, nitrobenzene).
  • Compounds with a hydroxy group are called phenols (e.g., phenolamine).
• What are the key properties of benzene that contribute to its stability?

  • Delocalized electron structure.
  • Equal bond lengths of 139 picometers.
  • Lower enthalpy change of hydrogenation compared to theoretical values.
• What are the two main reactions of benzene that students need to know?

  1. Friedel-Crafts reaction
  2. Nitration reaction
• How does the stability of benzene affect its reactivity?

  • Benzene is stable due to its delocalized structure.
  • It resists addition reactions that would disrupt this stability.
  • Undergoes electrophilic substitution instead.
• What is the significance of bond enthalpy in understanding benzene's stability?

  • Bond enthalpy measures the energy required to break bonds.
  • Benzene's lower enthalpy change indicates greater stability.
  • More energy is needed to break benzene's bonds compared to cyclohexene.
• Why does benzene not react easily?

  Benzene has a stable structure that makes it resistant to reactions.
• What type of reaction do benzene undergoes?

  Benzene undergoes electrophilic substitution reactions.
• 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 and dye production?

  Benzene is crucial for the synthesis of many drugs and dyes.
• What is the role of the acyl group in Friedel-Crafts acylation?

  The acyl group weakens the benzene structure, making it easier to modify.
• What is required to react with benzene in Friedel-Crafts acylation?

  A strong electrophile is required to react with benzene.
• What is the purpose of using a halogen carrier in Friedel-Crafts acylation?

  The halogen carrier generates a stronger electrophile for the reaction.
• What is the halogen carrier used in Friedel-Crafts acylation?

  Aluminium chloride (AlCl3) is the halogen carrier used.
• What happens to the acyl chloride when it reacts with the halogen carrier?

  The halogen carrier accepts electrons and forms a carbocation.
• What is formed after the electrophile attacks the benzene ring?

  An unstable intermediate with a positive charge is formed.
• What must be done to restore the stability of the benzene ring after the electrophile attack?

  The electrons from the C-H bond must return to reform the benzene structure.
• What is the product of Friedel-Crafts acylation?

  A phenyl ketone is produced from the reaction.
• What is the purpose of keeping the temperature below 55 degrees Celsius during nitration?

  To prevent multiple nitration of the benzene ring.
• What is the electrophile formed in the nitration of benzene?

  The nitronium ion (NO2+) is the electrophile formed.
• What is the catalyst used in the nitration of benzene?

  Sulfuric acid (H2SO4) acts as the catalyst.