Introduction to Amines for JEE Main

The chapter Amines is an important part of Class 12 Organic Chemistry and carries considerable weight in JEE Main examinations. Amines are derivatives of ammonia in which one or more hydrogen atoms are replaced by alkyl or aryl groups.

A good understanding of amines helps students tackle nucleophilic substitution reactions, Hoffmann rearrangement, and diazotization reactions – all common in JEE Main.

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Classification of Amines

Amines are classified based on the number of alkyl/aryl groups attached to nitrogen:

• Primary (1°): R–NH₂

• Secondary (2°): R₂NH

• Tertiary (3°): R₃N

Amines can also be aliphatic or aromatic. Understanding classification is essential for predicting reactivity.

Nomenclature of Amines

IUPAC rules include:

• Name the longest carbon chain

• Identify the position of –NH₂

• Use suffix “amine”

Trivial names like methylamine, aniline are also important for JEE Main.

Structure of Amines

• Nitrogen in amines is sp³ hybridized

• Lone pair on nitrogen makes amines basic

• Bond angles slightly less than 109.5° due to lone pair repulsion

Understanding structure explains basicity and reactivity.

Methods of Preparation of Amines

Important methods include:

• Reduction of nitro compounds (aromatic amines)

• Reduction of nitriles

• Hofmann bromamide degradation (for primary amines)

• Gabriel phthalimide synthesis

Preparation-based questions are common in JEE Main.

Physical Properties of Amines

• Boiling point increases with hydrogen bonding

• Soluble in water due to polarity

• Distinct fishy odor

These properties are influenced by hydrogen bonding and molecular structure.

Chemical Properties of Amines

Amines are nucleophilic and basic, and undergo several reactions:

• Reaction with acids → Formation of ammonium salts

• Acylation → Formation of amides

• Reaction with nitrous acid (primary amines) → Diazotization

Basicity of Amines

• Aliphatic amines are generally more basic than ammonia

• Aromatic amines (like aniline) are less basic due to delocalization of lone pair

• Solvent effects (like water, DMSO) influence basicity

Basicity comparison questions often appear in JEE Main.

Diazotization of Aromatic Amines

• Primary aromatic amines react with NaNO₂ + HCl at 0–5°C

• Forms diazonium salts

• Diazotization is key for azo coupling and Sandmeyer reactions

Named reactions from diazonium salts are frequently asked.

Hofmann Bromamide Reaction

• Converts primary amides to primary amines with one fewer carbon atom

• Important for both mechanism-based questions and synthetic pathways

Carbylamine Reaction

• Tests the presence of primary amines

• Formation of isocyanides (smelly compounds)

• Commonly asked in JEE Main MCQs

Aromatic Amines

• Examples: Aniline

• Undergo electrophilic substitution

• –NH₂ is ortho/para directing

• Reactivity affected by electron-withdrawing groups

Comparison Between Aliphatic and Aromatic Amines

• Aliphatic amines are more basic

• Aromatic amines are less basic due to conjugation

• Reaction behavior differs for nucleophilic substitution and diazotization

Comparison-based questions are common in exams.

Applications of Amines

• Pharmaceuticals (e.g., sulfa drugs)

• Dyes and pigments

• Agrochemicals

• Synthetic intermediates

Application-based questions may appear in JEE Main.

Important JEE Main Preparation Tips for Amines

• Focus on mechanism of diazotization and Hofmann reactions

• Memorize key reagents and conditions

• Compare basicity of different amines

• Solve previous year JEE Main questions

Why Study Amines from Studentbro.in?

Studentbro.in offers:

• Step-by-step reaction mechanisms

• Concept-based explanations

• MCQs and PYQs for practice

• Exam-oriented study material

All content strictly follows the latest JEE Main syllabus.

Conclusion

The Amines chapter is a conceptual and scoring topic in Class 12 Chemistry for JEE Main. With clarity on preparation, reactions, and mechanism, students can confidently solve both MCQs and application-based questions.

Studentbro.in provides structured, exam-focused content to master amines efficiently.