Phenol reacts with bromine water in carbon disulphide at low temperature to give (a) O-bromophenol (b) O- and P-bromophenols (c) P-bromophenol (d) \(2,4,6\) -tribromophenol

Phenol, often known as carbolic acid, is an aromatic compound characterized by a hydroxyl group (-OH) attached to a benzene ring. This simple structure belies the rich chemistry that phenol participates in due to the influence of the hydroxyl group on the aromatic ring.

One of the most notable features of phenol is its acidity; it is more acidic than alcohols and can form phenoxide ions when it loses a proton. This acidity is due to the stabilization of the phenoxide ion by resonance structures where the negative charge can be delocalized over the aromatic system. The aromatic ring of phenol is highly reactive to electrophilic aromatic substitution reactions because the electron-donating nature of the -OH group increases the electron density on the ring, especially at the ortho and para positions.

The bromination of phenol is a specific case of electrophilic aromatic substitution where a bromine atom replaces a hydrogen atom on the aromatic ring. Due to the activating effect of the hydroxyl group, phenol is particularly reactive towards bromine.

During the bromination process, phenol can react without the need for a strong Lewis acid catalyst because the -OH group makes the benzene ring much more susceptible to attack by the bromine molecule, which acts as an electrophile. In electrophilic aromatic substitution, the -OH group directs the incoming electrophile to the ortho and para positions relative to itself, enhancing the likelihood of substitution at these sites. Unlike benzene, which requires harsh conditions for bromination, phenol readily undergoes bromination even at low temperatures, indicating its heightened reactivity.

2,4,6-Tribromophenol is the product formed when phenol undergoes bromination and all three hydrogen atoms at the ortho and para positions are replaced by bromine atoms. The result is a compound with bromine atoms at the 2, 4, and 6 positions of the benzene ring. This is a dramatic illustration of the directing effect of the hydroxyl group on the benzene ring of phenol.

The particular conditions of the bromination reaction, using bromine water and carbon disulfide at low temperature, are optimized to facilitate the formation of the tribrominated product. The low temperature helps to control the reaction rate and prevent further oxidation or side reactions. The carbon disulfide serves as a non-polar solvent to assist the reaction, as bromine is more soluble in non-polar solvents. The result is the formation of a compound that has significant applications in the synthesis of other chemicals, as well as being a useful antiseptic and a precursor to various flame retardants.