Question

Differentiate between primary, secondary and tertiary amines. (Write chemical equations)

Hint:

Always use nitrous acid test to distinguish between primary, secondary and tertiary amines in organic chemistry.

Answer 1

Step 1: Understanding the classification.
Amines are classified based on the number of alkyl or aryl groups attached to the nitrogen atom.
Step 2: Differences with examples.
\begin{enumerate} \item
Primary amine (1°): Nitrogen atom is attached to one alkyl/aryl group.
General formula: R–NH$_2$
Example: Methylamine (CH$_3$NH$_2$)
Reaction:
\[ CH_3NH_2 + HNO_2 \rightarrow CH_3OH + N_2 \uparrow + H_2O \] \item
Secondary amine (2°): Nitrogen atom is attached to two alkyl/aryl groups.
General formula: R$_2$–NH
Example: Dimethylamine ((CH$_3$)$_2$NH)
Reaction:
\[ (CH_3)_2NH + HNO_2 \rightarrow (CH_3)_2NNO + H_2O \] \item
Tertiary amine (3°): Nitrogen atom is attached to three alkyl/aryl groups.
General formula: R$_3$–N
Example: Trimethylamine ((CH$_3$)$_3$N)
Reaction:
\[ (CH_3)_3N + HNO_2 \rightarrow (CH_3)_3NNO \] \end{enumerate} Conclusion:
- Primary amines give alcohol and nitrogen gas with nitrous acid.
- Secondary amines form nitrosoamines.
- Tertiary amines form soluble salts or nitrosonium complexes.