6.1.5

• phenol

  
• Phenol

  Phenol is the first member of a type of aromatic compounds where a hydroxyl group (-OH) is attached directly to an aromatic ring.

  • If the hydroxyl group is attached to an alkyl chain on the aromatic ring then the compound is no longer a phenol derivative. It would be described as an aromatic alcohol
• Phenol 2

  • Phenol is a weak acid, as it partially dissociates in water. The chemical equilibrium can be shown in a balanced chemical equation: C6H5OH + H2O = H3O+ + C6H5O-
  • As a weak acid, phenol will react with strong bases to form a salt and water. A balanced chemical equation illustrates the reaction between phenol and sodium hydroxide: C6H5OH + NaOH → C6H5O-Na+ + H2O

  Phenol is an acid because it reacts with strong bases such as NaOH.

  However, it is a weak acid because it does not react with carbonates.

  Phenol will not react with weak bases such as sodium carbonate.
• Reactivity

  • Phenol is more reactive than benzene.

  → This is due to the p-orbital electrons from the oxygen of the hydroxyl group adding to the delocalised electrons of the aromatic ring + so the pi-system of the aromatic ring becomes more nucleophilic.

  • The increase in electron density allows the aromatic ring in phenol to be more susceptible to electrophilic attack as it can induce a dipole in non-polar molecules
• Reactivity 2

  • Non-bonding electrons on the oxygen atom in the phenol group are drawn into the benzene ring.

  → The lone pair becomes part of the delocalisation, increasing the electron density in the ring.

  For example, as the aromatic ring in phenol is more electron-dense, it can induce a dipole in the non-polar bromine molecule. So phenol can undergo direct halogenation, unlike benzene