You are given benzene, conc. H₂SO₄ and NaOH. Write the equations for the preparation of phenol using these reagents.
Phenol can be prepared from benzene, conc. H₂SO₄ and NaOH through the benzenesulphonic acid method.
Step 1: Sulphonation of benzene Benzene is sulphonated with conc. H₂SO₄ to form benzene sulphonic acid.
Step 2: Fusion with molten NaOH Benzene sulphonic acid is converted to sodium phenoxide on heating with molten sodium hydroxide.
Step 3: Acidification Acidification of sodium phenoxide gives phenol.
Explanation
The question specifically asks for preparation of phenol using benzene, conc. H₂SO₄ and NaOH. According to the textbook context under 'From benzenesulphonic acid', benzene is first sulphonated with oleum (or conc. H₂SO₄) to form benzene sulphonic acid, which is then heated with molten NaOH to form sodium phenoxide. Finally, acidification yields phenol. This is a three-step process involving sulphonation, alkali fusion, and acidification.
Solution Steps
Step 1: Sulphonation - Benzene reacts with conc. H₂SO₄ to form benzene sulphonic acid
Step 2: Alkali fusion - Benzene sulphonic acid heated with molten NaOH gives sodium phenoxide
Step 3: Acidification - Sodium phenoxide is acidified to obtain phenol