Concept:
This is an example of an azo coupling reaction, where aromatic diazonium salts react with activated aromatic compounds like phenol or aniline to form azo compounds (\(-N=N-\)).
Step 1: Type of reaction.
Benzenediazonium chloride reacts with phenol in an alkaline medium.
Step 2: Role of the alkaline medium.
In basic solution:
Phenol ionizes to form phenoxide ion.
The phenoxide ion is strongly activated, making it more reactive toward electrophilic substitution.
Step 3: Position of coupling.
Coupling predominantly occurs at the para position relative to the –OH group due to reduced steric hindrance.
Step 4: Product formed.
The product of the reaction is p-hydroxyazobenzene, an azo dye.
The reaction is represented as:
\[
C_6H_5N_2^+Cl^- + C_6H_5OH \xrightarrow{OH^-}
\text{p-Hydroxyazobenzene} + HCl
\]
Final Answer:
\[
\text{p-Hydroxyazobenzene (Azo dye)}
\]
