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Science Class 12 - Amines Notes

Comprehensive study notes for Class 12 - Amines olympiad preparation

Amines

Welcome to the chapter on Amines for Class 12. In this chapter, you will learn about the structure, classification, nomenclature, preparation, properties, and uses of amines. By the end of this chapter, you will understand the importance of amines in organic chemistry and their applications in daily life.

Introduction

Amines are organic compounds derived from ammonia (NH3) by replacing one or more hydrogen atoms with alkyl or aryl groups. They are important in biology, industry, and medicine.

Classification of Amines

  • Primary (1°) amine: One hydrogen of NH3 is replaced (RNH2).
  • Secondary (2°) amine: Two hydrogens are replaced (R2NH).
  • Tertiary (3°) amine: All three hydrogens are replaced (R3N).

Nomenclature of Amines

  • Common names: Based on alkyl groups attached to nitrogen (e.g., methylamine, dimethylamine).
  • IUPAC names: Replace the ‘e’ of the parent alkane with ‘amine’ (e.g., ethanamine for CH3CH2NH2).

Preparation of Amines

  • Reduction of nitro compounds: Nitrobenzene + H2/Pd or Sn/HCl → Aniline
  • Ammonolysis of alkyl halides: R-X + NH3 → RNH2 + HX
  • Gabriel phthalimide synthesis: Used for preparing primary amines.
  • Hofmann bromamide reaction: Amide + Br2 + NaOH → Primary amine

Physical Properties of Amines

  • Lower aliphatic amines are gases; higher ones are liquids or solids.
  • Amines have a fishy odor.
  • They form hydrogen bonds, so lower amines are soluble in water.

Chemical Properties of Amines

  • Basic character: Amines act as bases and form salts with acids.
  • Alkylation: Amines react with alkyl halides to form higher amines.
  • Acylation: Amines react with acid chlorides to form amides.
  • Reaction with nitrous acid: Primary aliphatic amines give alcohols; aromatic amines give diazonium salts.
  • Carbylamine reaction: Primary amines react with chloroform and KOH to form isocyanides (foul smell).

Uses of Amines

  • Used in the manufacture of dyes, drugs, and polymers.
  • Aniline is used to make rubber, dyes, and medicines.
  • Amines are found in many biological molecules (e.g., amino acids, hormones).

Practice Questions

  1. Classify the following as primary, secondary, or tertiary amine: (a) CH3NH2 (b) (CH3)2NH (c) (CH3)3N
  2. Write the IUPAC name of C2H5NH2.
  3. How is aniline prepared from nitrobenzene?
  4. What happens when a primary amine reacts with nitrous acid?
  5. Name one use of amines in daily life.

Challenge Yourself

  • Explain the difference between Gabriel phthalimide synthesis and Hofmann bromamide reaction.
  • Describe the carbylamine reaction and its significance.

Did You Know?

  • Serotonin and adrenaline, important hormones in our body, are amines!
  • Some amines are used as local anesthetics in medicine.

Glossary

  • Amine: An organic compound derived from ammonia by replacing hydrogen atoms with alkyl or aryl groups.
  • Diazonium salt: A compound formed by the reaction of aromatic amines with nitrous acid.
  • Carbylamine reaction: A test for primary amines that produces isocyanides with a foul smell.

Answers to Practice Questions

  1. (a) Primary, (b) Secondary, (c) Tertiary
  2. Ethanamine
  3. By reduction of nitrobenzene with H2/Pd or Sn/HCl.
  4. Primary aliphatic amines give alcohols and nitrogen gas; aromatic amines form diazonium salts.
  5. Used in making medicines, dyes, and rubber.

Understanding amines helps you explore the world of organic chemistry and its applications in real life!

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