Question

Write chemical equations of the method of preparation of diazonium salt and its four chemical reactions.

Hint:

Diazonium salts are highly reactive and are used in synthetic organic chemistry for producing aryl halides and azo dyes.

Answer 1

Step 1: Preparation of Diazonium Salt Diazonium salts are prepared by diazotization, where an aromatic primary amine reacts with sodium nitrite (\( NaNO_2 \)) and hydrochloric acid (HCl) at low temperatures (0–5°C). \[ C_6H_5NH_2 + HNO_2 + HCl \rightarrow C_6H_5N_2^+Cl^- + 2H_2O \] Step 2: Reactions of Diazonium Salt \begin{enumerate} \item Sandmeyer Reaction (Halogenation) \[ C_6H_5N_2^+Cl^- + CuCl \rightarrow C_6H_5Cl + N_2 \] \item Gattermann Reaction (Aryl Halide Formation) \[ C_6H_5N_2^+Cl^- + CuBr \rightarrow C_6H_5Br + N_2 \] \item Coupling Reaction (Formation of Azo Compounds) \[ C_6H_5N_2^+Cl^- + C_6H_5OH \rightarrow C_6H_5N=N-C_6H_4OH + HCl \] \item Reduction to Phenylhydrazine \[ C_6H_5N_2^+Cl^- + H_2 \xrightarrow{Sn/HCl} C_6H_5NHNH_2 + HCl \] \end{enumerate}