Q.Give the reagents and conditions necessary to prepare phenol from
a. Chlorobenzene
b. Benzene sulfonic acid.

Part a. From chlorobenzene (Dow process, section 11.4.2). Chlorobenzene is fused with NaOH under forcing conditions: 623 K (high temperature) and 300 atm (high pressure). This displaces the ring chlorine, forming sodium phenoxide (C6H5-O-Na). The sodium phenoxide is then treated with dilute HCl (H3O+), which protonates the phenoxide ion and liberates phenol.

Reagents/conditions: (i) NaOH, 623 K, 300 atm;

(ii) dilute HCl.

Part b. From benzene sulfonic acid (section 11.4.2). Benzene sulfonic acid (C6H5-SO3H) is first neutralised with NaOH (an ordinary acid-base reaction) to give sodium benzene sulfonate (C6H5-SO3Na). This salt is then fused with SOLID NaOH at 573 K, a more forcing alkali-fusion step that displaces the sulfonate group entirely and gives sodium phenoxide. Finally, acidifying with dilute HCl liberates phenol. …

Reciting the exact reagents and conditions of the Dow process and the benzene-sulfonic-acid route from section 11.4.2, keeping the …

• Omitting the specific temperature/pressure conditions (623 K/300 atm for the Dow process; 573 K for the sulfonate fusion), which the question specifically asks for. …