Phenol
Phenol C₆H₅OH is a weak acid, stronger than water and ethanol but weaker than carboxylic acids: the phenoxide ion is stabilised by delocalisation of the O⁻ charge into the ring. It reacts with Na and NaOH but not with carbonates. A lone pair on oxygen also delocalises into the ring, activating it: phenol decolourises bromine water at room temperature without a catalyst, giving a white precipitate of 2,4,6-tribromophenol, and nitrates with dilute HNO₃. Halogenoarenes (e.g. chlorobenzene) are unreactive to nucleophiles because the halogen lone pair delocalises into the ring, strengthening the C–X bond.
≈ 40 min