Question

How are the following conversions carried out?
1.Chlorobenzene to benzoic acid
2.Chlorobenzene to benzene

Answer 1

Hint: We have to know that chlorobenzene is a haloarene. It is an aromatic substituted compound that contains a chloro group attached to a benzene ring. We can obtain Benzoic acid from chlorobenzene by treating sodium and methyl chloride in the presence of dry ether with chlorobenzene, and the product is formed. The formed product is then oxidized to form benzoic acid. The benzoic acid is then reacted with sodium hydroxide and calcium oxide to form benzene.

Complete answer:
1.Formation of benzoic acid from chlorobenzene:
We know that chlorobenzene is a haloarenes (aryl halides) that contains a chloro group linked to benzene rings. We can obtain benzoic acid from chlorobenzene when we treat chlorobenzene with sodium and methyl chloride in the presence of ether to form toluene. Toluene undergoes oxidation using oxidizing agents such as potassium permanganate, and sulfuric acid to form benzoic acid. We can write the chemical equation as,

2.Formation of benzene from chlorobenzene:
We know that chlorobenzene is a haloarenes (aryl halides) that contains a chloro group linked to benzene rings. We can obtain benzene from chlorobenzene when we treat chlorobenzene with sodium and methyl chloride in the presence of ether to form toluene. Toluene undergoes oxidation using oxidizing agents such as potassium permanganate, and sulfuric acid to form benzoic acid. Benzoic acid is then treated with sodium to form sodium phenoxide. The formed sodium phenoxide is then treated with sodium hydroxide and calcium oxide to form benzene. We can write the chemical reaction as,

Note:
We have to remember that the chlorobenzene could be converted to benzoic acid using Grignard reagent and also using iodide-silica gel catalyst. The carboxylation of chlorobenzene with carbon monoxide and water at high pressure in the presence of iodide-silica gel catalyst gives benzoic acid as the product. We can write the chemical reaction as,
${C_6}{H_5}Cl + CO + {H_2}O \to {C_6}{H_5}COOH + HCl$
We can also prepare benzene from chlorobenzene, by treating chlorobenzene with hydrogen in the presence of sodium hydroxide/Ni-Al alloy. We can write the chemical reaction as,
${C_6}{H_5}Cl + 2\left[ H \right]\underset{{NaOH}}{\overset{{Ni - Al\,Alloy}}{\longleftrightarrow}}{C_6}{H_6} + HCl$
We can also convert chlorobenzene to sodium phenoxide, convert sodium phenoxide to phenol, then convert phenol to benzene using zinc dust.