Step 1: Identify the starting material. The starting material is aniline \( C_6H_5NH_2 \), an aromatic primary amine. Step 2: Diazotisation of aniline. Aniline reacts with \( NaNO_2 \) and \( HCl \) at 0-5 degrees C (273-278 K) to give benzene diazonium chloride: \[ C_6H_5NH_2 + NaNO_2 + 2HCl \rightarrow C_6H_5N_2^+Cl^- + NaCl + 2H_2O \] Step 3: Apply the Sandmeyer reaction with CuCl. Benzene diazonium chloride reacts with cuprous chloride (CuCl) in HCl. The diazonium group is replaced by chlorine: \[ C_6H_5N_2^+Cl^- + CuCl \rightarrow C_6H_5Cl + N_2 \] This gives chlorobenzene. Step 4: Identify the major product. The major product of diazotisation followed by Sandmeyer reaction with CuCl is chlorobenzene. Step 5: Rule out alternatives. CuBr gives bromobenzene. KI gives iodobenzene. CuCN gives benzonitrile. Only CuCl gives chlorobenzene. Step 6: State the answer. The major product is chlorobenzene (option 2). \[ \boxed{\text{Chlorobenzene}} \]
