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Amines RNH2 or ArNH2


Amine " amine salt. Aliphatic and aromatic amines react similarly.
Reagent: dilute hydrochloric acid, or other mineral acid.
Conditions: at r.t.

CH3CH2NH2 + HCl " CH3CH2NH3+ + Cl -

aniline_chloride.gif (1832 bytes)

Amines that are insoluble in water will dissolve in hydrochloric acid, and be precipitated with alkali.

Alkanes & alkenes
Aldehydes and ketones

Carboxylic acids
Acyl chlorides
Nitro compounds


Primary amine " diazonium salt
Reagents: nitrous acid, produced from sodium nitrite and dilute hydrochloric acid.
Conditions: Sodium nitrite is dissolved in water and added slowly to a solution of the amine in excess concentrated hydrochloric acid at 0o-10oC. Below 0oC the reaction is too slow; above 10oC the diazonium compound will decompose.

Only diazonium salts from primary aromatic amines are synthetically useful, since aliphatic diazonium ions rapidly decompose:

C6H5NH3 + + HNO2 " C6H5N2+ + 2H2O


Coupling reaction of a diazonium salt with a phenol to give an azo dye:
Reagents: a phenol such as phenol itself, or 2-naphthol, dissolved in sodium hydroxide solution.
Conditions: at r.t.

With phenol:

phenol_coupling.gif (2281 bytes)

With 2-naphthol:

naphthol_coupling.gif (2958 bytes)

2-naphthol                                                       phenylazo-2-naphthol (red)


JRG Beavon 2002