Phenol

Phenol, C₆H₅OH, has an OH group bonded directly to a benzene ring. It is not an alcohol: in phenylmethanol, C₆H₅CH₂OH, the OH is on a side chain, so that compound behaves as an alcohol.Phenol is a white crystalline solid at room temperature with a low melting temperature. It is moderately soluble in water, because its OH group forms hydrogen bonds with water molecules.Acidity: phenol is a weak acid. It partially dissociates in water to form the phenoxide ion:
C₆H₅OH ⇌ C₆H₅O⁻ + H⁺
It is a stronger acid than ethanol but a weaker acid than carboxylic acids such as ethanoic acid. The negative charge on the phenoxide ion is partly delocalised into the benzene ring, which stabilises the ion.Reaction with sodium hydroxide: phenol reacts with NaOH to form a salt, sodium phenoxide, and water:
C₆H₅OH + NaOH → C₆H₅ONa + H₂ONo reaction with carbonates: phenol is too weak an acid to react with sodium carbonate or sodium hydrogencarbonate, so there is no fizzing. This distinguishes phenol from carboxylic acids.Uses: phenol and its derivatives are used to make antiseptics and disinfectants, resins and plastics.Worked example: how can phenol, ethanol and ethanoic acid be told apart? Add NaHCO₃(aq): only ethanoic acid fizzes, giving CO₂. Of the other two, only phenol reacts with NaOH(aq), forming sodium phenoxide; ethanol is too weak an acid to react.