In the laboratory, phenols are prepared from chlorobenzene by fusing it with NaOH at 623 K, followed by acidification of the produced sodium phenoxide. From benzenesulphonic acid, phenol is obtained by sulphonating benzene with oleum, converting the resulting benzene sulphonic acid to sodium phenoxide, and acidifying the sodium salt.
Describe the laboratory preparation of phenols from chlorobenzene and benzenesulphonic acid.
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The laboratory preparation of phenols from chlorobenzene involves the Sandmeyer reaction. Chlorobenzene is treated with sodium hydroxide (NaOH) and copper(I) chloride (CuCl) to generate phenol. The reaction proceeds through the formation of diazonium salt, followed by replacement of the chlorine atom with a hydroxyl group. Benzenesulphonic acid can be converted to phenol through a similar process. It undergoes nucleophilic substitution with sodium hydroxide, leading to the formation of phenol and sodium bisulfite. Both methods provide a route for the preparation of phenols by introducing the hydroxyl group to the benzene ring.