Question

Which of the following is(are) example(s) of Sandmeyer reaction?
\[\begin{align}
  & \text{A}\text{. }{{\text{C}}_{\text{6}}}{{\text{H}}_{\text{5}}}{{\text{N}}^{\text{+}}}\text{C}{{\text{l}}^{\text{-}}}\to {{\text{C}}_{\text{6}}}{{\text{H}}_{\text{5}}}\text{Cl} \\
 & \text{B}\text{. }{{\text{C}}_{\text{6}}}{{\text{H}}_{\text{5}}}{{\text{N}}^{\text{+}}}\text{C}{{\text{l}}^{\text{-}}}\to {{\text{C}}_{\text{6}}}{{\text{H}}_{\text{5}}}\text{OH} \\
 & \text{C}\text{. }{{\text{C}}_{\text{6}}}{{\text{H}}_{\text{5}}}{{\text{N}}^{\text{+}}}\text{C}{{\text{l}}^{\text{-}}}\to {{\text{C}}_{\text{6}}}{{\text{H}}_{\text{5}}}\text{CN} \\
 & \text{D}\text{. }{{\text{C}}_{\text{6}}}{{\text{H}}_{\text{5}}}{{\text{N}}^{\text{+}}}{{\text{I}}^{\text{-}}}\to {{\text{C}}_{\text{6}}}{{\text{H}}_{\text{5}}}\text{I} \\
\end{align}\]

Answer 1

Hint:Sandmeyer reaction involves free radical mechanism for the synthesis of aryl halides. Direct substitution can only be achieved using the Sandmeyer reaction. Transformations like hydroxylation, trifluoromethylation, cyanation and methylation can be achieved by Sandmeyer reaction.

Complete answer:
The above question belongs to the concept of Haloalkanes and haloarenes. Haloalkanes and haloarenes are the hydrocarbons which contain a halogen group which includes chlorine, iodine, bromine. The halogen gets attached to the hydrocarbon by replacing one or more atoms from that compound. The basic difference in haloalkanes and haloarenes is that haloalkanes are derived from alkanes or the open chain of hydrocarbons but the haloarene compounds are derived from the aromatic compounds or alkenes. The above question includes Sandmeyer’s reaction. The basic definition of Sandmeyer reaction is addition of halogen in other words Sandmeyer reaction is a chemical reaction which is used for the synthesis of aryl halides from aryl diazonium salts with the help of a copper which act as a catalyst. It is a substitution reaction which involves radical nucleophilic aromatic substitution. In this substitution the nucleophile which is rich in electron attacks on a positively charged electrophile so that the leaving group can be replaced such as halide from an aromatic ring. Nucleophilic aromatic substitution is of six types, in this case radical nucleophilic substitution is occurring. The diazonium compounds used in the synthesis of aryl halide are prepared using nitric acid and amines.
Now in option (B) and (C) the reaction which is occurring doesn’t provide us with aryl halide in the product but in case of option (A) and (D) the end product after the reaction is an aryl halide.

Therefore, option (A) and (D) are the correct answers.

Note:
The mechanism followed in the Sandmeyer reaction is the electron transfer mechanism. The disadvantage of Sandmeyer’s reaction is that Iodo Benzene cannot be synthesised or formed through this reaction because of its large size.