Aromatic Amine Formation (Edexcel A Level Chemistry): Revision Note

Aromatic Amine Formation

• Phenylamine is an organic compound consisting of a benzene ring and an amine (NH₂) functional group

  • Phenylamine is sometimes known as aminobenzene and aniline

• Nitrobenzene, C₆H₅NO₂, can be reduced to phenylamine, C₆H₅NH₂, according to the following two-stage reaction:

The two-stage reduction reaction of nitrobenzene to phenylamine

Stage 1 - Reduction of nitrobenzene

• Nitrobenzene, C₆H₅NO₂, is reacted with tin, Sn, and concentrated hydrochloric acid, HCl

  • Tin and hydrochloric acid act as reducing agents

• The reaction mixture is heated under reflux in a boiling water bath

• In the acidic conditions the phenylamine is protonated, forming phenylammonium ions, C₆H₅NH₃⁺

Stage 2 - Formation of phenylamine

• The phenylammonium ions, C₆H₅NH₃⁺, are deprotonated by the addition of excess sodium hydroxide solution, NaOH (aq)

• Equation for stage 1: C₆H₅NO₂ + 6[H] + H⁺ → C₆H₅NH₃⁺ + 2H₂O

• Equation for stage 2: C₆H₅NH₃⁺ + OH^- → C₆H₅NH₂ + H₂O

• Overall: C₆H₅NO₂ + 6[H] → C₆H₅NH₂ + 2H₂O