Question

Complete the following equation:

Hint:

Azo coupling: Diazonium salt + Activated aromatic ring → Azo dye (\(-N=N-\)).

Answer 1

Concept: This is an example of an
azo coupling reaction. Aromatic diazonium salts react with activated aromatic compounds like phenol or aniline to form azo compounds (\(-N=N-\)).
Step 1: Reaction type. Benzenediazonium chloride reacts with phenol in alkaline medium.
Step 2: Role of alkaline medium. In basic solution:

• Phenol forms phenoxide ion.
• Phenoxide is strongly activated toward electrophilic substitution.

Step 3: Position of coupling. Coupling occurs mainly at the
para position relative to the –OH group due to less steric hindrance.
Step 4: Product formed. The product is
p-hydroxyazobenzene (an azo dye). \[ C_6H_5N_2^+Cl^- + C_6H_5OH \xrightarrow{OH^-} p\text{-Hydroxyazobenzene} + HCl \]
Final Answer: \[ \text{p-Hydroxyazobenzene (Azo dye)} \]