Notes On Diazonium Salts - CBSE Class 12 Chemistry
Diazonium salts have the general formula Where X = Cl-, Br-, HSO4-, BF4-...etc Aryl diazonium salts are used as intermediates to synthesise a wide variety of organic compounds. Primary alkyl diazonium ions are not very stable. They decompose easily and tend to be explosive when dry. Aryl diazonium salts are stable only for short times at low temperatures. Resonance structures help to stabilise the ion by delocalising the positive charge around the aromatic ring. Aryl diazonium salts are produced by reacting aniline with nitrous acid, generated in situ (must be prepared freshly before use) at 273-278 K. Ex: In the Sandmeyer reactions, diazonium groups are replaced by chloride, bromide or cyanide in the presence of copper (I) ions. In the Gatterman reactions, diazonium groups are replaced with Chlorine (or) Bromine by treating the diazonium salt solution with haloacid in the presence of copper powder. Diazonium group may be replaced by iodine by treatment with potassium iodide. The Schiemann reaction is a method for the production of aryl fluorides. In reductive deamination, the diazonium group is replaced by hydrogen after treatment with mild reducing agents such as hypophosphorous acid (or) ethanol. In nitration reactions, the diazonium group is replaced by an -NO2 group. Phenols can be prepared from diazonium salts by hydrolysing with dilute sulphuric acid and heating. Azo coupling reactions occur when diazonium salts react with phenol (or) aniline.

#### Summary

Diazonium salts have the general formula Where X = Cl-, Br-, HSO4-, BF4-...etc Aryl diazonium salts are used as intermediates to synthesise a wide variety of organic compounds. Primary alkyl diazonium ions are not very stable. They decompose easily and tend to be explosive when dry. Aryl diazonium salts are stable only for short times at low temperatures. Resonance structures help to stabilise the ion by delocalising the positive charge around the aromatic ring. Aryl diazonium salts are produced by reacting aniline with nitrous acid, generated in situ (must be prepared freshly before use) at 273-278 K. Ex: In the Sandmeyer reactions, diazonium groups are replaced by chloride, bromide or cyanide in the presence of copper (I) ions. In the Gatterman reactions, diazonium groups are replaced with Chlorine (or) Bromine by treating the diazonium salt solution with haloacid in the presence of copper powder. Diazonium group may be replaced by iodine by treatment with potassium iodide. The Schiemann reaction is a method for the production of aryl fluorides. In reductive deamination, the diazonium group is replaced by hydrogen after treatment with mild reducing agents such as hypophosphorous acid (or) ethanol. In nitration reactions, the diazonium group is replaced by an -NO2 group. Phenols can be prepared from diazonium salts by hydrolysing with dilute sulphuric acid and heating. Azo coupling reactions occur when diazonium salts react with phenol (or) aniline.

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