Question

Starting from Aniline how will you prepare Benzene Diazonium Chloride?

Answer 1

Conversion of Aniline into Benzene Diazonium Chloride:

Step 1: Formation of nitrous acid

• Nitrous acid is typically produced by acidifying aqueous Sodium Nitrite solutions with a mineral acid.
• Acidification is typically carried out at ice temperatures, and the ${\mathrm{HNO}}_2$ is consumed in situ.
• Nitrous acid is highly unstable and decomposes quickly.
• $\underset{\mathrm{Sodium}\mathrm{Nitrate}}{{\mathrm{NaNO}}_2\left(\mathrm{l}\right)}+\underset{\mathrm{Hydrochloric}\mathrm{acid}}{\mathrm{HCl}\left(\mathrm{l}\right)}⟶\underset{\mathrm{Nitrous}\mathrm{acid}}{{\mathrm{HNO}}_2\left(\mathrm{l}\right)}+\underset{\mathrm{Sodium}\mathrm{Chloride}}{\mathrm{NaCl}\left(\mathrm{l}\right)}$

Step 2: Formation of diazonium salt

• Aniline is a primary arylamine in which an amino functional group is substituted for one of the benzene hydrogens.
• Diazotization of Aniline with ${\mathrm{NaNO}}_2/\mathrm{HCl}$ gives Benzene diazonium chloride.
• Diazotization reaction mechanism generally involves the usage of Nitrous acid (${\mathrm{HNO}}_2$) and another acid in the treatment of Aromatic Amines in order to yield the diazonium salt.
• On treatment with ${\mathrm{NaNO}}_2$ and $\mathrm{HCl}$ at $273-278\mathrm{K}$, aniline produces Benzenediazonium Chloride, with $\mathrm{NaCl}$and ${\mathrm{H}}_2\mathrm{O}$ as by-products.