azo dyes

Question

Azo dyes are prepared by:

RankGuru · Accepted Answer

**Azo Coupling** is an electrophilic aromatic substitution reaction where a diazonium cation acts as an electrophile.
- Reaction: $ArN_2^+ + Ar'-H 	o Ar-N=N-Ar' + H^+$
- The second aromatic ring ($Ar'$) must be strongly activated by groups like **$-OH$ (Phenol)** or **$-NH_2$ (Aniline)**.
- Conditions: Phenols couple in weakly basic solution (forming orange dyes), whereas amines couple in weakly acidic solution (forming yellow dyes).
- The resulting **Azo compounds** have an extended conjugated $\pi$ system, making them intensely colored dyes.

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azo dyes

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