CIE A Level Chemistry复习笔记7.6.6 Azo Compounds

• Azo (or diazonium) compounds are organic compounds that have an R₁-N=N-R₂ group
• They are often used as dyes and are formed in a coupling reaction between the diazonium ion and an alkaline solution of phenol

Azo compounds are characterized by the presence of an R₁-N=N-R₂ group

Coupling of benzenediazonium chloride with phenol in NaOH

• Azo compounds can be formed from the coupling reaction of a benzenediazonium chloride salt with alkaline phenol
• Making an azo dye is a multi-step process

Formation of azo compounds table

Reaction mechanism of the formation of azo compounds

• The delocalised electrons in the π bonding systems of the two benzene rings are extended through the -N=N- which acts as a bridge between the two rings
• As a result of the delocalisation of electrons throughout the compound, azo compounds are very stable

Making other azo dyes

• Other dyes can be formed via a similar route as described above
• For example, the yellow dye can be formed from the coupling reaction between benzenediazonium chloride and C₆H₅N(CH₃)₂instead of phenol (C₆H₅OH)

The yellow azo dye is formed via a coupling reaction between benzenediazonium chloride and C₆H₅N(CH₃)₂