Phenol is prepared by Dow's process. Conditions involved in Dow’s process of preparing phenol are

The Dow's process is a significant industrial method for preparing phenol. In this process, phenol is synthesized from chlorobenzene under specific conditions. Chlorobenzene is relatively unreactive towards the aromatic nucleophilic substitution (ArSN) reaction because of its stability due to resonance. The C-Cl bond in chlorobenzene exhibits partial double bond character, making it challenging to break.

Conditions Required in Dow's Process

To overcome the resistance of chlorobenzene in the Dow's process and convert C6H5-Cl to C6H5-OH (phenol), harsh reaction conditions are necessary:

• The reaction is carried out at a high temperature of approximately 623 K.
• High pressure ranging from 300 atm to 320 atm is required to facilitate the reaction.

Why These Conditions Are Necessary

In the Dow's process, the strong resonance stabilization in chlorobenzene makes the C-Cl bond harder to cleave. This partial double bond character adds rigidity to the molecule. As a result, extreme conditions of temperature and pressure are necessary to drive the reaction and successfully produce phenol.

Key Steps in Dow's Process

1. Chlorobenzene (C6H5-Cl) reacts with aqueous sodium hydroxide (NaOH) under the specified high temperature and pressure.
2. The reaction leads to the replacement of the chlorine atom with a hydroxyl group, resulting in phenol (C6H5-OH).

Importance of Dow's Process

The Dow's process is widely used in industrial applications for synthesizing phenol, a critical compound in the production of plastics, resins, and other chemical intermediates. Understanding the reaction conditions and molecular behavior of chlorobenzene helps in optimizing this method for large-scale phenol production.