NCERT Class 12 Chemistry Chemistry-II: Chapter 4 — Amines
This chapter introduces Amines, an important class of organic compounds derived from ammonia by replacing hydrogen atoms with alkyl or aryl groups. It covers the structure of amines, describing them as having a pyramidal geometry due to the sp3 hybridized nitrogen atom with an unshared electron pair. The chapter classifies amines into primary, secondary, and tertiary based on the number of hydrogen atoms replaced. It also details the nomenclature of amines using both common and IUPAC systems, including naming conventions for simple, mixed, aliphatic, and aromatic amines. The importance of amines and diazonium salts as intermediates in synthesizing various compounds like medicines, fibers, polymers, dyes, and drugs is highlighted, emphasizing their role in organic chemistry and biological systems.
Quick info
| Board | CBSE / NCERT |
|---|---|
| Class | Class 12 |
| Subject | Chemistry |
| Book | Chemistry-II |
| Chapter | Chapter 4 — Amines |
| Language | English |
| PDF type | NCERT Textbook |
| Session | CBSE 2026 |
| Reading time | 4 minutes |
| Word count | 672 |
Learning outcomes
- Describe amines as derivatives of ammonia with a pyramidal structure.
- Classify amines as primary, secondary, and tertiary.
- Name amines using common names and the IUPAC system.
- Understand the importance of amines and diazonium salts in synthesis.
Vocabulary
| Word | Meaning |
|---|---|
| Alkyl group | A univalent radical derived from an alkane by removing one hydrogen atom. |
| Aryl group | A univalent radical derived from an aromatic hydrocarbon by removing one hydrogen atom. |
| Primary amine | An amine where the nitrogen atom is bonded to one alkyl or aryl group and two hydrogen atoms. |
| Secondary amine | An amine where the nitrogen atom is bonded to two alkyl or aryl groups and one hydrogen atom. |
| Tertiary amine | An amine where the nitrogen atom is bonded to three alkyl or aryl groups. |
| IUPAC system | International Union of Pure and Applied Chemistry system for naming chemical compounds. |
| Diazonium salts | Salts containing the functional group R−N2+X−, where R is an organic group and X is an anion. |
| Pyramidal structure | A molecular geometry where atoms are arranged in a pyramid shape. |
| sp3 hybridization | Hybridization of one s and three p orbitals to form four sp3 hybrid orbitals. |
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Practice questions
- What is the hybridization of the nitrogen atom in amines? Answer: The nitrogen atom in amines is sp3 hybridized.
- Classify the following amine: CH3-NH-CH2CH3 Answer: This is a secondary amine.
- How are primary amines named in the IUPAC system? Answer: Primary amines are named as alkanamines, derived by replacing the 'e' of alkane with 'amine'.
- Give an example of a tertiary amine. Answer: Trimethylamine ((CH3)3N) or Triethylamine ((CH3CH2)3N) are examples of tertiary amines.
Practice MCQs
Q1. Amines are derivatives of which molecule?
Explanation: Amines are formed by replacing one or more hydrogen atoms of ammonia with alkyl or aryl groups.
Q2. What is the geometry of amines?
Explanation: Due to the presence of an unshared pair of electrons on the nitrogen atom, amines exhibit a pyramidal geometry.
Q3. Which type of amine has the nitrogen atom bonded to three alkyl or aryl groups?
Explanation: Tertiary amines are characterized by the nitrogen atom being bonded to three organic substituents.
Q4. In the IUPAC system, CH3NH2 is named as:
Explanation: In the IUPAC system, CH3NH2 is named methanamine, derived from methane by replacing 'e' with 'amine'.
Q5. Which of the following is a common use of amines mentioned in the text?
Explanation: The text explicitly states that the chief commercial use of amines is as intermediates in the synthesis of medicines and fibres.
Frequently asked questions
What are amines?
Amines are organic compounds derived from ammonia by replacing one or more hydrogen atoms with alkyl or aryl groups.
How are amines classified?
Amines are classified as primary (1°), secondary (2°), and tertiary (3°) depending on the number of hydrogen atoms replaced by alkyl or aryl groups in ammonia.
What is the structure of the nitrogen atom in amines?
The nitrogen atom in amines is trivalent, sp3 hybridized, and carries an unshared pair of electrons, resulting in a pyramidal geometry.
What is the difference between simple and mixed amines?
Simple amines have identical alkyl or aryl groups attached to the nitrogen atom, while mixed amines have different alkyl or aryl groups.
How are amines named in the IUPAC system?
In the IUPAC system, primary amines are named as alkanamines. For secondary and tertiary amines, the locant 'N' is used to designate substituents attached to the nitrogen atom.
What are diazonium salts and why are they important?
Diazonium salts are intermediates containing the R−N2+X− functional group. They are important in the synthesis of a variety of aromatic compounds, including azo dyes.
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NCERT Class 12 Chemistry — Chemistry-II — Chapter 4 — Amines. Verified by NCERT Help Editorial Team. Reviewed on 29 Jul 2026. Last updated 10 Aug 2026.