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How is phenol prepared from (1) benzeene sulphonic acid 92) aniline (diazotization) (March'15) and (3) chlorobenzene and steam? |
Answer» Solution :(1) Preparation of phenol from benzene sulphonic acid: Benzene sulphonic acid is treated with the requistite quantity of soda as `(Na_(2)CO_(3))` or `NaOH` and the solution is EVAPORATED to obtained sodium benzene sulphonate salt. Dry sodium benzene sulphonate is fused with an excess of caustic soda `(NaOH)` at about `573K` when sodium phenioxide is formed. The fused mass of sodium phenoxide on treatment with DILUTE `H_(2)SO_(4)` gives phenol. (2) Preparation of phenol from ANILINE (diazotization): When aniline is treated with sodium nitrite and hydrochloric acid at low TEMPERATURE `(0^(@)C-5^(@)C)` benzene diazonium chloride is formed. This reaction is called diazotization. An aqueous solution of benzene diazonium chloride on warming with dil. `H_(2)SO_(4)` gives phenol.  (3) PREPARATIONOF phenol from chlorobenzene and steam: Chlorobenzene is treated with steam in the presence of calcium phosphate or silica `(SiO_(2))` as a catalyst when phenol is obtained. 
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