Phenol reacts with bromine water to give white ppt of 2,4,6-tribromophenol.
Phenol in the presence of water is converted into the phenoxide ion (C6H5−O−) which is a strong activating species. Hence tribromo-substitution occurs.
Bromine is added to a non-polar solvent like CS2 or CCl4 to form monobromo phenol.
Phenol reacts with conc. HNO3 to form 2,4,6-trinitrophenol.
Dil. HNO3 is used to get mononitro phenols.
Phenol reacts with chloroform (CHCl3) in base (NaOH or KOH etc.) to form salicylaldehyde.
If we use CCl4 (carbon tetrachloride) instead of chloroform, salicylic acid is formed.
The reaction of phenoxide ion with CO2 followed by acidification yields salicylic acid. This reaction is known as Kolbe's reaction.
Benzenediazonium salt reacts with phenol in weakly alkaline medium at low temperature (0-5° C) to form coloured products called azo dyes. This reaction is known as coupling reaction.