Preparation of phenol from benzene sulphonic acid :
Benzene sulphonic acid is neutralized with the requisite quantity of soda ash (Na2CO3) or NaOH and the solution is evaporated to obtain sodium benzene sulphonate salt.
Dry sodium benzene sulphonate is fused with an excess of caustic soda (NaOH) at about 573 K when sodium phenoxide is formed.
The fused mass of sodium phenoxide on treatment with dilute HCl gives phenol.
