Introduction to Amines – Class 12 Chemistry
What are Amines?
Amines are organic compounds derived from ammonia (NH3) by replacing one or more hydrogen atoms with alkyl or aryl groups. They contain a nitrogen atom bonded to carbon and/or hydrogen atoms. Due to the presence of a lone pair of electrons on nitrogen, amines are basic and nucleophilic in nature.
Classification of Amines (Class 12)
- Primary (1°) Amine: One carbon-containing group attached (e.g., CH3NH2)
- Secondary (2°) Amine: Two carbon groups attached (e.g., (CH3)2NH)
- Tertiary (3°) Amine: Three carbon groups attached (e.g., (CH3)3N)
- Quaternary Ammonium Compounds: Four organic groups attached to nitrogen with + charge (e.g., (CH3)4N+Cl−)
Types of Amines
- Aliphatic Amines: Derived from alkanes (e.g., ethylamine)
- Aromatic Amines: Derived from aromatic rings (e.g., aniline)
- Cyclic Amines: Nitrogen atom is part of a ring (e.g., piperidine)
Physical Properties
- Lower amines → gases/liquids with fishy odor.
- 1° & 2° amines → hydrogen bonding → higher boiling points.
- Solubility in water decreases as alkyl/aryl group size increases.
Basic Character of Amines
Amines act as bases due to lone pair on nitrogen. Basicity depends on:
- Type of amine (1°, 2°, 3°)
- Electron-donating/withdrawing substituents
- Solvent effects (more basic in non-aqueous solvents)
Importance of Amines
- Present in biological systems (amino acids, neurotransmitters like dopamine)
- Used in drugs, dyes, pesticides, polymers
- Building blocks in organic & pharmaceutical chemistry
Quick Revision Table (Class 12)
| Property | 1° Amine | 2° Amine | 3° Amine |
|---|---|---|---|
| Hydrogen Bonding | Strong | Moderate | None |
| Basicity (aqueous) | Moderate | Highest | Lowest |
| Boiling Point | High | Moderate | Low |
Practice Questions (Class 12)
- Which amine is most basic in aqueous solution?
a) Methylamine ✅
b) Dimethylamine
c) Trimethylamine
d) Aniline - Why do 3° amines have lowest boiling points among isomers?
FAQs
Q1. Why are amines basic?
Because of lone pair of electrons on nitrogen that can accept a proton (H+).
Q2. Which is stronger base – aliphatic or aromatic amine?
Aliphatic amines are stronger bases than aromatic amines (due to resonance in aromatic compounds reducing electron density on N).
Q3. अमीन्स (Amines) को हिंदी में क्या कहते हैं?
अमोनिया (NH3) से व्युत्पन्न कार्बनिक यौगिकों को अमीन कहते हैं।
Amines are versatile in Class 12 Organic Chemistry — from medicines to dyes, their role is foundational.
Useful for JEE and NEET prep.
