Simulation · Chemistry · Class 12
Keep the diazonium salt cold
From the lesson Diazonium salts: making and handling in Amines. Change the values and watch what happens.
Keep the diazonium salt coldChemistry · Class 12
The idea behind it
NCERT §9.7–9.8
- Diazonium salts have the formula R–N₂⁺X⁻, where R is an aryl group and X⁻ may be Cl⁻, Br⁻, HSO₄⁻, BF₄⁻ and so on. The –N₂⁺ group is the diazonium group.
- Names add 'diazonium' to the parent hydrocarbon and then name the anion: C₆H₅N₂⁺Cl⁻ is benzenediazonium chloride and C₆H₅N₂⁺HSO₄⁻ is benzenediazonium hydrogensulphate.
- Primary aliphatic amines give very unstable alkyldiazonium salts. Arenediazonium salts last for a short time in cold solution (273–278 K); resonance with the ring explains their extra stability.
- Diazotisation is the conversion of a primary aromatic amine into its diazonium salt. Benzenediazonium chloride is made from aniline and nitrous acid (NaNO₂ + HCl) at 273–278 K: C₆H₅NH₂ + NaNO₂ + 2HCl → C₆H₅N₂⁺Cl⁻ + NaCl + 2H₂O.
- Being unstable, the salt is usually used as soon as it is made rather than stored.
- Benzenediazonium chloride is a colourless crystalline solid, readily soluble in water. It is stable in the cold, reacts with water on warming and decomposes easily when dry. Benzenediazonium fluoroborate is insoluble in water and stable at room temperature.