Reaction of Primary Amines with Nitrous Acids

Reaction of nitrous acid with Aromatic Primary amines

At 273 - 278 K, atomic primary amines react with sodium nitrite and dilute HCl, to give aromatic diazonium salts. For example, aniline forms benzene diazonium chloride.

Aromatic diazonium salts are stable only at low temperature. Hence at higher temperature, aromatic primary amine gives phenols.

Reaction of nitrous acid with Aromatic Primary amine

Aliphatic diazonium salts are highly unstable and hence alcohols are obtained when aliphatic primary amines are reacted with nitrous acid.

properties of amines

Chemical properties of amines

In most of its reaction, amines act as a nucleophile or a base due to lone pair on nitrogen. In aromatic amines, due to resonance, the -NH2 group make the ring more susceptible to electrophilic substitution at ortho and para position.

Important reactions of amines are classified as :

 1. Salt formation

Amines are soluble in mineral acids and carboxylic acids, due to the formation of soluble ammonium salts.

RNH2 + HCl  ------->  RNH3+ Cl-

C6H5NH2 --------> C6H5NH3+ Cl-

2. Alkylation

Alkyl halides when react with primary or secondary amines undergo nucleophilic substitution. When HX is removed, secondary or tertiary amine formed will again reacts with alkyl halide froming tertiary amine and finally quaternary ammonium salt.


3. Acylation

4. Reaction with carbonyl compounds

5. Carbylamine reaction

6. Reaction with nitrous acids

With nitrous  acid primary, secondary and tertiary amines react differently and give different product. Hence this reaction can be used to distinguish primary, secondary and tertiary amines from each other.

For more visit Physical Properties of Amine