Question

Which of the following reactions can be used for the conversion of chlorobenzene to benzene?
(a)- ${{C}_{6}}{{H}_{5}}-Cl+2[H]\xrightarrow[NaOH]{Ni-Alloy}{{C}_{6}}{{H}_{6}}+HCl$
(b)- ${{C}_{6}}{{H}_{5}}-Cl\xrightarrow[ether]{Mg}{{C}_{6}}{{H}_{5}}-MgCl\xrightarrow{{{H}_{2}}O}{{C}_{6}}{{H}_{6}}$
(c)- Both of the above
(d)- ${{C}_{6}}{{H}_{5}}-Cl+{{H}_{2}}O\xrightarrow{150-{{200}^{\circ }}C}{{C}_{6}}{{H}_{6}}+{{H}_{2}}S{{O}_{4}}$

Answer 1

Hint: Benzene is an aromatic compound having formula ${{C}_{6}}{{H}_{6}}$. Chlorobenzene can be converted into benzene by two methods. The products benzene and sulfuric acid are formed when the reactant is benzene sulfonic acid.

Complete step by step answer:
Chlorobenzene is an aromatic compound having chlorine at one of the carbon atoms in the ring. The formula of chlorobenzene is ${{C}_{6}}{{H}_{5}}-Cl$.
Benzene is an aromatic compound having formula ${{C}_{6}}{{H}_{6}}$.
Chlorobenzene can be converted into benzene by two methods. The methods are discussed below:
Haloarenes in presence of alkali can be converted into the corresponding arenes by reduction with nickel-aluminium alloy. So, the chlorobenzene can be converted into benzene by reduction with nickel-aluminium alloy in presence of sodium hydroxide.
${{C}_{6}}{{H}_{5}}-Cl+2[H]\xrightarrow[NaOH]{Ni-Alloy}{{C}_{6}}{{H}_{6}}+HCl$

When chlorobenzene is reacted with magnesium in the presence of ether, they form Grignard reagent. The formed Grignard reagent has the formula ${{C}_{6}}{{H}_{5}}-MgCl$. This compound on hydrolysis forms benzene. The overall reaction will be:
${{C}_{6}}{{H}_{5}}-Cl\xrightarrow[ether]{Mg}{{C}_{6}}{{H}_{5}}-MgCl\xrightarrow{{{H}_{2}}O}{{C}_{6}}{{H}_{6}}$

In option (d)- ${{C}_{6}}{{H}_{5}}-Cl+{{H}_{2}}O\xrightarrow{150-{{200}^{\circ }}C}{{C}_{6}}{{H}_{6}}+{{H}_{2}}S{{O}_{4}}$

The products benzene and sulfuric acid are formed when the reactants are taken Benzene sulfonic acid and water is taken. The reaction is given below:
${{C}_{6}}{{H}_{5}}-S{{O}_{3}}H+{{H}_{2}}O\xrightarrow{150-{{200}^{\circ }}C}{{C}_{6}}{{H}_{6}}+{{H}_{2}}S{{O}_{4}}$

So, option (d) is wrong.
So, the correct answer is “Option C”.

Note: All the chemical reactions of chlorobenzene are nucleophilic substitution reactions. The haloarenes are less reactive than the haloalkanes towards the nucleophilic substitution reaction. Or we can say that haloarenes are more stable than haloalkanes.