Chemical Properties of Diazonium Salt Preparation and Properties

Chemical Properties of Diazonium Salt Preparation and Properties

The reactions of diazonium salts can be broadly divided into two categories :

  • Reaction involving displacement of Nitrogen.
  • Reaction involving retention of diazo group (Coupling reaction)

→ Nitrogen Substitution Reaction : In these reactions —N22Cl group is substituted by other atoni or group.

→ These group releases nitrogen gas from aromatic ring. Free nitrogen releases as a gas from the reaction mixture.

Chemical Properties of Diazonium Salt Preparation and Properties

→ SynthesIs of aryl halide : When benzene diazonium chloride react with Cu2Cl2 and HCl or Cu2 Br2 and HBr then (—N2Cl group) is replaced by —CI or —Br respectively. This reaction is called Sandmeyer reaction.

Chemical Properties of Diazonium Salt Preparation and Properties 1

→ Gatterniann Reaction It is a form of Sandmeyer’s reaction in which aromatic diazonium salt reacts with Cu/HCl, in presence of halogen acid and Cu powder to form aryl halide.

Chemical Properties of Diazonium Salt Preparation and Properties 2

Chemical Properties of Diazonium Salt Preparation and Properties 3

→ When benzene diazonium chloride is treated with fluoroboric acid, then benzene diazonium fluoroborate is precipitated which decomposes on heating and give flourobenzene.

Chemical Properties of Diazonium Salt Preparation and Properties 4

→ This reaction is known as Balz-Schiemann reaction. Benzene diazonium salt when boiled with potassium iodide solution forms iodobenzene.

Chemical Properties of Diazonium Salt Preparation and Properties 5

→ Synthesis of Nitro Compounds : Benzene diazonium chloride reacts with aqueous sodium nitrite solution in the presence of copper and forms nitrobenzene.

Chemical Properties of Diazonium Salt Preparation and Properties 6

→ Synthesis of Phenol : Benzene diazonium chloride on distillatión with steam gives phenol.

Chemical Properties of Diazonium Salt Preparation and Properties 7

Synthesis of Cyano Compound : Benzene diazonium chloride reacts with cuprous cyanide to form cyanobenzene.

Chemical Properties of Diazonium Salt Preparation and Properties 8

→ Synthesis of Thiol : Benzene diazonium chloride reacts with potassium hydrosuiphide, the thiophenol is formed.

Chemical Properties of Diazonium Salt Preparation and Properties 9

→ Oxidation : Mild reducing agents like hypophosphor ous acid or ethanol oxidised benzene diazonium chloride to benzene.

Chemical Properties of Diazonium Salt Preparation and Properties 10

→ Reduction Benzene diazomum chloride when reduced in the presence of SnCl2 and HCl, it gives phenyl hydrazine.

Chemical Properties of Diazonium Salt Preparation and Properties 11

→ If benzene diazonium chloride reduces with Zn and HCl then aniline is formed.

Chemical Properties of Diazonium Salt Preparation and Properties 12

→ Synthesis of Dlphenyl : Benzene cliazonium chloride when treated with benzene in the basic medium gives diphenyl.

Chemical Properties of Diazonium Salt Preparation and Properties 13

Coupling Reactions : The azo products obtained have an extended conjugate system having both the aromatic rings joined through the —N = N— bond.

These compounds are often coloured and are used as dyes.

These reaction are as follows :

→ Reaction with Aniline : Diazonium chloride reacts with aniline and form paraaminoazobenzene. It is an example of electrophobic reaction.

Chemical Properties of Diazonium Salt Preparation and Properties 14

→ Reation with Phenol : Benzene diazonium chloride reacts with pheno’ to form para hydroxyazo benzene.

Chemical Properties of Diazonium Salt Preparation and Properties 15

→ Reaction with β-Naphthol Diazonium chloride reacts with -naphtho1 to form red coloured phenylazo-β-naphthol dye.

Chemical Properties of Diazonium Salt Preparation and Properties 16

→ Reaction with Dimethyl Aniline : Dimethyl aniline reacts with benzene diazonium chloride to form p-Dimethylamino azo benzene.

Chemical Properties of Diazonium Salt Preparation and Properties 17

Chemistry Notes