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  • (a) Name the starting material used in the industrial preparation of phenol. (b) Write complete reaction for the bromination of phenol in aqueous and non-aqueous medium. (c) Explain why Lewis acid is not required in bromination of pheflol ?

(a) Name the starting material used in the industrial preparation of phenol.
(b) Write complete reaction for the bromination of phenol in aqueous and non-aqueous medium.
(c) Explain why Lewis acid is not required in bromination of phenol ?

Answers (1)

Solution: (a) The main initiating material used in the industrial preparation of phenol is Cumene (Isopropyl benzene)

(c) In the normal case scenario, Lewis acid is necessary to carry out the halogenation reaction, and FeBr_{3} is responsible for the polarisation of the halogen molecule. But when phenol is taken for halogenation reaction, due to its -OH group no activation agent is required as it is a high activation group present on the benzene ring. 

The mechanism involved is that phenoxide ion is given by phenol after ionisation in aqueous solution. And the presence of negative charge on the oxygen atom dictates it to give its electron to the benzene ring. This makes the ring trisubstituted product due to its high activation. But in non-polar solvents, phenol does not ionise to a greater extent. As a consequence, electrons are donated to a small extent by the -OH group. The ring is activated slightly only contributes to mono-substitution.

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