Consider the classic azo coupling reaction between benzene diazonium chloride and phenol in a slight — Aromatic Hydrocarbons Chemistry Question
Question
Consider the classic azo coupling reaction between benzene diazonium chloride and phenol in a slightly alkaline medium to form a highly colored azo dye. How many nitrogen atoms are directly participating in the continuous $\pi$ -conjugation bridge connecting the two aromatic rings in the final dye molecule?
Answer: 2
💡 Solution & Explanation
The coupling of a diazonium salt with phenol (at pH 9-10) yields p-hydroxyazobenzene. The two aromatic rings are joined by an azo linkage ($-N=N-$). This specific bridge consists of exactly 2 nitrogen atoms, which are $sp^2$ hybridized and provide the extended $\pi$ -conjugation responsible for the compound's intense color.
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