How will you prepare the following compounds from benzene? You may use any inorganic reagent and any organic reagent having not more than one carbon atom (i) Methyl benzoate (ii) m-Nitrobenzoic acid (iii) p-Nitrobenzoic acid (iv) Phenylacetic acid (v) p-Nitrobenzaldehyde.
Benzene undergoes Friedel-Crafts alkylation with CH₃Cl/AlCl₃ to form toluene. Toluene is oxidised with KMnO₄/KOH followed by acidification (H₃O⁺) to give benzoic acid. Benzoic acid reacts with methanol (CH₃OH) in presence of acid to form methyl benzoate.
Benzene undergoes nitration with HNO₃/H₂SO₄ to form nitrobenzene. Nitrobenzene undergoes Friedel-Crafts alkylation with CH₃Cl/AlCl₃ to give m-nitrotoluene (NO₂ group is meta-directing). Oxidation with KMnO₄/KOH followed by H₃O⁺ gives m-nitrobenzoic acid.
Benzene undergoes Friedel-Crafts alkylation with CH₃Cl/AlCl₃ to form toluene. Toluene undergoes nitration with HNO₃/H₂SO₄ to give p-nitrotoluene (CH₃ group is ortho-para directing). Oxidation with KMnO₄/KOH followed by H₃O⁺ gives p-nitrobenzoic acid.
Benzene undergoes Friedel-Crafts alkylation with CH₃Cl/AlCl₃ to form toluene. Side-chain chlorination with Cl₂/hv gives benzyl chloride. Benzyl chloride reacts with KCN to form benzyl cyanide. Hydrolysis with H₃O⁺ gives phenylacetic acid.
Benzene undergoes Friedel-Crafts alkylation with CH₃Cl/AlCl₃ to form toluene. Nitration with HNO₃/H₂SO₄ gives p-nitrotoluene. Selective oxidation using CrO₂Cl₂ (Etard reaction) converts the methyl group to aldehyde, giving p-nitrobenzaldehyde.
Explanation
This question tests understanding of electrophilic aromatic substitution reactions, directing effects of substituents, and oxidation reactions. Key concepts include: (i) Friedel-Crafts alkylation introduces alkyl groups onto benzene; (ii) the directing nature of substituents—CH₃ is ortho-para directing while NO₂ is meta-directing; (iii) KMnO₄ oxidises alkyl side chains to carboxylic acids; (iv) side-chain chlorination followed by cyanide substitution and hydrolysis extends carbon chain; (v) Etard reaction selectively oxidises methyl to aldehyde.