Amines
1.0 Introduction
2.0 Preparation of Amines
2.1 Nucleophilic substitution
2.2 Reduction of Nitro Compounds
2.3 Reduction of Nitriles
2.4 Reduction of Amides
3.0 Physical Properties
4.0 Basic Nature of Amines
5.0 Reactions of Amines
5.1 Reaction of ${1^ \circ }$ and ${2^ \circ }$ amines with aldehydes and ketones
5.2 Acylation Reaction
5.3 Carbylamine Reaction
5.4 Reaction with Nitrous Acid
5.5 Substitution Reactions of Aryl Diazonium Salts
5.6 Electrophilic substitution reaction of Aniline
5.4 Reaction with Nitrous Acid
2.2 Reduction of Nitro Compounds
2.3 Reduction of Nitriles
2.4 Reduction of Amides
5.2 Acylation Reaction
5.3 Carbylamine Reaction
5.4 Reaction with Nitrous Acid
5.5 Substitution Reactions of Aryl Diazonium Salts
5.6 Electrophilic substitution reaction of Aniline
Nitrous acid, $HNO_2$, is a weak, unstable acid formed from $NaNO_2$ and a strong acid like $HCl$.
In the presence of acid, nitrous acid decomposes to $^{+}NO$, the nitrosonium ion. This electrophile then goes on to react with the nucleophile nitrogen atom of amines to form diazonium salts $(RN_2^+Cl^-)$ from ${1^ \circ }$ amines and $N$-nitrosamines $(R_2NN=O)$ from ${2^ \circ }$ amines.
- Primary aliphatic amines react with nitrous acid to form aliphatic diazonium salts which being unstable, liberate nitrogen gas quantitatively and alcohols. Quantitative evolution of nitrogen is used in estimation of amino acids and proteins. Alkyl Dizonium salt is formed in the reaction as shown below.
- With secondary Amines, the reaction takes place as follows.
- Aromatic amines react with nitrous acid at low temperatures $(273-278\ K)$ to form diazonium salts as shown in the reaction.
