Distinction Between 1°, 2°, and 3° Amines – Class 12 Organic Chemistry

In Class 12 Organic Chemistry, amines are an important functional group. They are classified into Primary (1°), Secondary (2°), and Tertiary (3°) amines depending on how many alkyl or aryl groups are attached to the nitrogen atom.

Primary (1°) Amine

Structure: R–NH₂

Examples: Methylamine, Aniline

Secondary (2°) Amine

Structure: R–NH–R′

Examples: Dimethylamine, Diphenylamine

Tertiary (3°) Amine

Structure: R–N(R′)–R″

Examples: Trimethylamine, Triphenylamine

Chemical Distinction Tests (Class 12 Exams)

1. Hinsberg Test

Used in Class 12 practical exams to distinguish amines.

• 1° Amine: Soluble sulfonamide in alkali.
• 2° Amine: Insoluble sulfonamide.
• 3° Amine: No reaction.

2. Nitrous Acid Test

• 1° Amine: Evolves N₂ gas.
• 2° Amine: Forms N-nitroso compound.
• 3° Amine: No visible reaction.

3. Acylation Reaction

1° & 2° amines form amides with acyl chlorides; 3° amines do not.

Quick Revision Table (Class 12 Chemistry)

Property	1° Amine	2° Amine	3° Amine
Structure	R–NH2	R–NH–R′	R–N(R′)–R″
Hinsberg Test	Soluble	Insoluble	No Reaction
Nitrous Acid	Gas Evolution	N-Nitroso	No Reaction
Acylation	Yes	Yes	No
N–H Bonds	2	1	0

Practice Questions – Class 12 Chemistry

MCQs

1. Which amine reacts with nitrous acid to evolve nitrogen gas?
   a) Primary ✅
   b) Secondary
   c) Tertiary
   d) None
2. Which amine does not undergo acylation?
   a) Primary
   b) Secondary
   c) Tertiary ✅
   d) All

True / False

1° amines give soluble sulfonamides in Hinsberg test. True ✅

3° amines evolve nitrogen gas with nitrous acid. False ❌

Fill in the Blanks

Primary amines have ___ N–H bonds. Answer: 2

Tertiary amines have ___ N–H bonds. Answer: 0

FAQs – Class 12 Amines

Q1. Which test is used to distinguish 1°, 2°, and 3° amines in Class 12 practical exams?

Hinsberg test and nitrous acid test are commonly used.

Q2. Why don’t tertiary amines undergo acylation?

They lack an N–H bond, which is necessary for acylation.