Phenols

• Phenols are more acidic than alcohols due to the resonance stabilization of the phenoxide ion.
• Phenol is an aromatic compound with an –OH group bonded directly to a benzene ring
• Phenol is weakly acidic; it is more acidic than aliphatic alcohols but less than carboxylic acids
• Phenol’s acidity is due to the lone pair of electrons on the oxygen overlapping with the π electron system of the ring, causing the hydrogen ion to be lost more easily, forming the phenoxide ion
• Phenol is acidic enough to react with sodium hydroxide, but it does not react with sodium carbonate. Carboxylic acids react with both, so sodium carbonate can be used to distinguish between phenols and carboxylic acids
• Acidity order: Carboxylic acids > Phenols > Alcohols
• Phenol reacts by electrophilic substitution due to the delocalised electron system
• Phenol reacts with bromine water by the substitution of 3 hydrogen atoms to form 2,4,6-tribromophenol, which forms as a white precipitate and decolourises the orange bromine water
• Phenols react with ethanoyl chloride to form aromatic esters, such as phenyl ethanoate, in addition-elimination reactions
• Tests to identify the phenol group:

  • Reaction with bromine water: produces a white precipitate and decolourises the bromine water
  • Reaction with iron(III) chloride solution: gives a purple colour when yellow iron(III) chloride solution is added to phenol