Electrophilic Substitution Reactions of Phenol

Bromination

Phenol reacts with bromine water to give white ppt of 2,4,6-tribromophenol.

Reason for tribromo substitution

Phenol in the presence of water is converted into the phenoxide ion (C₆H₅−O⁻) which is a strong activating species. Hence tribromo-substitution occurs.

Monobromo phenol

Bromine is added to a non-polar solvent like CS₂ or CCl₄ to form monobromo phenol.

Nitration

Phenol reacts with conc. HNO₃ to form 2,4,6-trinitrophenol.

Dil. HNO₃ is used to get mononitro phenols.

Reimer-Tiemann reaction

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.

Kolbe's reaction

The reaction of phenoxide ion with CO₂ followed by acidification yields salicylic acid. This reaction is known as Kolbe's reaction.

Coupling 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.

Conversion