Benzene diazonium chloride and Resorcinol Reaction

The reaction between benzene diazonium chloride and resorcinol yields an orange-red dye. This is due to the formation of an azo compound, which is a compound containing a nitrogen-nitrogen double bond (-N=N-) linked to two aromatic rings.

Mechanism of Reaction

1. Diazotization: Benzene diazonium chloride reacts with hydrochloric acid to form diazonium salt.

C6H5N2Cl + HCl → C6H5N2Cl2

2. Coupling: The diazonium salt then reacts with resorcinol in an acidic medium to form an azo compound.

C6H5N2Cl2 + C6H4(OH)2 → C12H8N2O2 + 2HCl

Where C12H8N2O2 is the orange-red dye formed.

Explanation

Resorcinol contains two hydroxyl (-OH) groups that can react with benzene diazonium chloride in the presence of an acid to form an azo compound. This reaction is known as coupling. The nitrogen-nitrogen double bond (-N=N-) in the azo compound is responsible for its color. The presence of the electron-donating hydroxyl groups on the aromatic ring of resorcinol increases the electron density on the ring, making it more susceptible to attack by the diazonium ion.

Conclusion

The reaction between benzene diazonium chloride and resorcinol yields an orange-red dye due to the formation of an azo compound. This reaction is widely used in the textile industry for dyeing fabrics.