Question

In the reaction sequence compound X is

A. chlorobenzene
B. benzene
C. toluene
D. biphenyl methane

Answer 1

Chlorination is the process through which the addition of chlorine by the hydrogen replacement takes place. The formation of DDT or Dichloro diphenyl trichloroethane takes place by the reaction between chloral and mono chloro substituted compounds.

Complete step by step answer:
- In the given question, we have to identify the compound X which undergoes further reaction.
- As we can see that the final product consists of two aromatic rings and also the compound reacts with chlorine.
-The compound X will undergo chlorination reaction in which the addition of chlorine will take place in the presence of $\text{FeC}{{\text{l}}_{3}}$, which act as a catalyst to increase the rate of the reaction.
-Now, the product formed after the reaction with chlorine will be a monosubstituted benzene ring which is also known as chlorobenzene.
- The balanced reaction will be:

-Now, when this chlorobenzene undergoes further reaction with the $\text{CC}{{\text{l}}_{3}}(\text{CHO) and }{{\text{H}}_{2}}\text{S}{{\text{O}}_{4}}$.
- Here, the formation of chloral hydrate takes place firstly because the direct formation of chloral is not possible by the given reaction:
$\text{4C}{{\text{l}}_{2}}\text{ + }{{\text{C}}_{2}}{{\text{H}}_{5}}\text{OH + }{{\text{H}}_{2}}\text{O}\to \text{ C}{{\text{l}}_{2}}\text{CCH(OH}{{\text{)}}_{2}}\text{ + 5HCl}$

-Now, the chloral will react with sulphuric acid which will desiccate the chloral hydrate into chloral which will react with chlorobenzene and forms DDT.

        Chloral hydrate chloral  

- Here, now this chloral will react to form DDT i.e.

 Chloral Chlorobenzene DDT or Dichloro Diphenyl trichloroethane  

So, the complete reaction will be:

Therefore, compound X is benzene.
So, the correct answer is “Option B”.

Note: Chloral is mainly aldehyde which is chlorinated and used as a precursor for the synthesis of the DDT which is further used as an insecticide to kill the unwanted micro-organism. For chloral to use as a precursor, it is necessary to convert it into chloral hydrate.