Question

Which of the following is not related with Friedel crafts reaction?
A) Acylation
B) Reduction
C) Sulphonation
D) Nitration

Answer 1

Hint: Friedel crafts reaction is a type of electrophilic aromatic substitution reaction. Electrophilic aromatic substitution is an organic reaction in which an atom that is attached to an aromatic system which is usually hydrogen is replaced by an electrophile. Aromatic nitration, aromatic halogenation and aromatic sulfonation comes under this category.

Complete answer:
Friedel crafts reaction is not related to reduction. This is because it is a type of electrophilic aromatic substitution reaction. It generally proceeds by substitution by an acyl, nitro or sulpho group. When an aromatic benzene ring is treated with acyl chlorides in the presence of Lewis acids as catalyst then, acylation of the benzene ring takes place. This type of reaction is known as Friedel crafts acylation. When sulphuric acid is added as a substrate, sulphonation takes place and this type of reaction is also known as Friedel crafts sulfonation. In the same way, Friedel crafts nitration takes place, when the substituted group is a nitro group. However, reduction does not take place in Friedel crafts reaction.

The ${H^ + }$ ions, with an oxidation number of $ + 1$, are reduced to ${H_2}$, with an oxidation number of zero, in the reaction:
\[Zn\left( s \right){\text{ }} + {\text{ }}2{H^ + }\left( {aq} \right){\text{ }} \to {\text{ }}Z{n^{2 + }}\left( {aq} \right){\text{ }} + {\text{ }}{H_2}\left( g \right)\]

Additional information:
Electrophilic aromatic substitution reaction is a type of organic reaction in which an atom attached to the aromatic ring is replaced by an electrophile. The atom which is replaced is usually hydrogen. The electrophile can be groups like acyl, nitro etc.
Friedel crafts reactions are a set of electrophilic aromatic substitution reactions which are grouped together on the basis of the type of electrophile. For example, if acyl group is substituted in the aromatic ring system then, such a reaction is termed as Friedel crafts acylation.

Hence the correct answer is option ‘D’.

Note: It should be noted that in reduction of the aromatic ring system such as benzene, the benzene ring is reduced to a saturated ring which is not evident in any of the Friedel crafts reactions. Hence, reduction is not involved in Friedel crafts reaction.