Benzenediazonium chloride undergoes a facile electrophilic aromatic substitution coupling reaction with phenol to form p-hydroxyazobenzene, an orange dye. What is the optimal necessary pH environment

Question

Benzenediazonium chloride undergoes a facile electrophilic aromatic substitution coupling reaction with phenol to form p-hydroxyazobenzene, an orange dye. What is the optimal necessary pH environment for this specific transformation to occur efficiently?

Prashant Kotian · Accepted Answer

Correct answer: C. Diazonium cations are extremely weak electrophiles. To successfully couple with phenol, the phenol must be converted into the much more nucleophilic phenoxide ion. This is achieved in a mildly basic medium, specifically at a pH of 9-10. A highly basic medium (pH 14) would destroy the diazonium salt by converting it to a diazotate anion.

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