WK17

• Explain the term carbonyl compound.

  Compound containing an aldehyde or ketone functional group
• Describe a test to show that a compound contains either aldehyde or ketone functional group.

  Add 2,4-DNPH

  1. Add 2,4-DNPH

  2. Red/orange/yellow solid formed
• Explain how the crystals from the test above can be used to confirm the identity of a specific carbonyl compound.

  1. Filter the precipitate
  2. Purify by recrystallisation and allow the crystals to dry
  3. Measure the melting point of crystals and compare to database of known values.
• Describe the evidence for the delocalized model of benzene.

  1. Bromine does not react with benzene.
  2. The enthalpy change of hydrogenation of benzene is less exothermic than anticipated.
  3. All C-C bonds in benzene have the same length.
• Describe the bonding in the delocalized model of benzene.

  1. One delocalised pi bond
  2. Containing 6 delocalised electrons between 6 carbon atoms
  3. Formed by the sideways overlap of six p-orbitals
  4. Above and below the plane of the ring
• Describe the bonding in the Kekule model of benzene.

  1. Three localised π bonds
  2. Each containing 2 electrons between 2 carbon atoms
  3. Formed by the sideways overlap of two neighbouring p-orbitals
  4. Above and below the plane of the ring
• Describe the similarities between the Kekule and delocalised model of benzene.

  1. π bond formed by the sideways overlap of p-orbitals
  2. above and below the plane of the ring