Discuss the mechanism of alkaline hydrolysisi of bromomethane.
How is carbolic acid prepared from chlorobenzene? What is the action of bromine water on carbolic acid?
Write chemical test to distinguish between carbolic acid and alcohol.

Explanation

Alkaline hydrolysis of bromomethane proceeds via bimolecular mechanism `(S_(N)2)`. Here hydroxide `(OH^(-))` ion behaves as nucleophile.

In this reaction a transition state is formed in which the entering hydroxyl group and both are partially bonded to the same carbon atom.
Preparation of carbolic acid (phenol) from chlorobenzene : Phenol is manufactured by heating chlorobenzene with 10% aqueous sodium hydroxide solution at about 623 K under 300 atmosphere in presence of copper salt (as catalyst) to form sodium phenoxide. The sodium salt when treated with dil. HCl gives phenol. This method is called Dow's process.

Action of bromine water on carbolic acid (Phenol) : Phenol reacts with bromine water (aqueous solution) to give a precipitate of 2, 4, 6-tribromo phenol.

However, if the reaction carried out in CS or `C Cl_(4)` at a low temperature a mixture of ortho and para bromophenol is obtained.

Chemical test to distinguish carbolic acid and alcohol.
1. Carbolic acid (phenol) turns blue litmus to red while alcohol do not have any effect on litmus solution.
2. Carbolic acid reacts with neutral `FeCl_(3)` solution to give chracteristic colours (blue, green, ciolet) on the other hand alcohol do not give any colour with neutral `FeCl_(3)` solution.