Question

\[ \mathrm{C_6H_5NH_2} \xrightarrow[\;273{-}278\,K\;]{\mathrm{HNO_2/HCl}} X \xrightarrow{\mathrm{Cu_2Cl_2}} Y \] Conversion of \(X\) to \(Y\) is called

• A. Gattermann reaction
• B. Gattermann--Koch reaction
• C. Stephen reaction
• D. Sandmeyer reaction

Hint:

\[ \boxed{ \mathrm{ArN_2^+X^-} \xrightarrow{\mathrm{CuCl,\ CuBr,\ CuCN}} \mathrm{ArCl,\ ArBr,\ ArCN} } \] This substitution of the diazonium group using cuprous salts is called the Sandmeyer reaction.

Answer 1

The Correct Option is D

Step 1: Formation of diazonium salt. Aniline reacts with nitrous acid in the presence of HCl at \(273{-}278\,K\) to form benzenediazonium chloride. \[ \mathrm{C_6H_5NH_2} \xrightarrow[\;273{-}278\,K\;]{\mathrm{HNO_2/HCl}} \boxed{\mathrm{C_6H_5N_2^+Cl^-}} \] Thus, \[ \boxed{X=\text{Benzenediazonium chloride}} \]

Step 2: Reaction with cuprous chloride. Benzenediazonium chloride reacts with cuprous chloride to form chlorobenzene. \[ \mathrm{C_6H_5N_2^+Cl^-} \xrightarrow{\mathrm{Cu_2Cl_2}} \mathrm{C_6H_5Cl} +\mathrm{N_2} \] Thus, \[ \boxed{Y=\text{Chlorobenzene}} \]

Step 3: Identify the reaction. Replacement of the diazonium group by halogen using cuprous salts is known as the \[ \boxed{\text{Sandmeyer reaction}.} \] Hence, \[ \boxed{(D)} \] is the correct answer.