What is a substitution reaction?
Give the reaction of chlorine with ethane and name the product formed.

Answer

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Hint: A substitution reaction also called single displacement reaction or single substitution reaction is a chemical reaction in which one functional group in a compound is replaced by another functional group. A good example of the replacement reaction is the halogenation reaction.

Complete answer:
In a substitution reaction, an atom or an ion or a group of atoms or ions in a molecule is replaced by another atom or ion or group. When ethane reacts with chlorine, we get hexachloroethane. Hexachloroethane is obtained after obtaining chloroethane, dichloroethane, trichloroethane, tetrachloroethane and pentachloroethane in the preceding steps. The reactions are shown below:

C_{2} H_{6} + C l_{2} \to C_{2} H_{5} C l + H C l

C_{2} H_{5} C l + C l_{2} \to C_{2} H_{4} C l_{2} + H C l

C_{2} H_{4} C l_{2} + C l_{2} \to C_{2} H_{3} C l_{3} + H C l

C_{2} H_{3} C l_{3} + C l_{2} \to C_{2} H_{2} C l_{4} + H C l

C_{2} H_{2} C l_{4} + C l_{2} \to C_{2} H C l_{5} + H C l

C_{2} H C l_{5} + C l_{2} \to C_{2} C l_{6} + H C l

Note:
The main product when ethane reacts with chlorine is chloroethane but other products are also obtained in small quantities. The formation of these other products reduces the yield of chloroethane. This is an example of substitution reaction because one of the hydrogen in ethane is replaced by an atom of chlorine. Along with chloroethane, hydrochloric acid is also formed in the first step of the reaction. The hydrogen in hydrochloric acid is the hydrogen of ethane which got replaced by the chlorine atom.