Complete Summary and Solutions for Amines – NCERT Class XII Chemistry Part II, Chapter 9 – Classification, Structure, Preparation, and Properties
Detailed summary and explanation of Chapter 9 'Amines' from the NCERT Class XII Chemistry Part II textbook, covering classification, nomenclature, preparation methods, physical and chemical properties of amines, including basicity and reactions, along with solved examples and all NCERT questions and answers.
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Amines
Chapter 9: Chemistry - Ultimate Study Guide | NCERT Class 12 Notes, Questions, Derivations & Quiz 2025
Full Chapter Summary & Detailed Notes - Amines Class 12 NCERT
Overview & Key Concepts
- Chapter Goal: Understand amines as ammonia derivatives, classification, nomenclature, preparation methods, physical/chemical properties, reactions. Exam Focus: Basicity trends, preparation, reactions like acylation; 2025 Updates: Biological importance (e.g., adrenaline). Fun Fact: Amines in dyes, drugs. Core Idea: Lone pair on N. Real-World: Surfactants, dyes. Expanded: All subtopics point-wise with evidence (e.g., Table 9.1 names), examples (e.g., aniline resonance), debates (basicity order).
- Wider Scope: From structure to diazonium salts; sources: Text, figures (9.1-9.2), tables.
- Expanded Content: Include reactions, diagrams; links (e.g., to haloalkanes); point-wise breakdown.
Introduction to Amines
- Definition: Ammonia derivatives, replace H with alkyl/aryl.
- Importance: In proteins, drugs, dyes.
- Applications: Adrenaline, novocain.
- Expanded: Evidence: Biological/synthetic; debates: Basicity; real: Surfactants.
9.1 Structure of Amines
- General: Pyramidal, sp3 N, lone pair.
- Expanded: Evidence: Fig 9.1; debates: Angle 108°; real: Like NH3.
Conceptual Diagram: Pyramidal Shape
Trimethylamine: N with three CH3, lone pair top.
9.2 Classification
- Types: 1°, 2°, 3° based on H replaced.
- Expanded: Evidence: Structures; debates: Simple/mixed; real: RNH2 vs R3N.
Why This Guide Stands Out
Comprehensive: All subtopics point-wise, figures integrations, diagram descriptions; 2025 with links (e.g., basicity), reactions analyzed for depth.
9.3 Nomenclature
- Common/IUPAC: Alkylamine/alkanamine.
- Expanded: Evidence: Table 9.1; debates: Aniline; real: N-substituents.
Exam Case Studies
Basicity order; preparation methods; Hinsberg test.
Key Themes & Tips
- Aspects: Structure, prep, props, reactions.
- Tip: Memorize reactions; diagrams for resonance; differentiate 1°/2°/3°.
Project & Group Ideas
- Model amine structures.
- Debate: Aliphatic vs aromatic basicity.
- Analyze drug amines.
Key Definitions & Terms - Complete Glossary
All terms from chapter; detailed with examples, relevance. Expanded: 30+ terms grouped by subtopic; added advanced like "carbylamine reaction", "Hinsberg test".
Amines
NH3 derivatives. Ex: CH3NH2. Relevance: Basic, nucleophilic.
Primary Amine
One alkyl/aryl. Ex: RNH2. Relevance: Carbylamine test.
Secondary Amine
Two groups. Ex: R2NH. Relevance: Liebermann test.
Tertiary Amine
Three groups. Ex: R3N. Relevance: No H on N.
Alkanamine
IUPAC aliphatic. Ex: Ethanamine. Relevance: Naming.
Benzenamine
Aniline IUPAC. Ex: C6H5NH2. Relevance: Aromatic.
Ammonolysis
NH3 + RX. Ex: Primary amine. Relevance: Preparation.
Gabriel Synthesis
Phthalimide + RX. Ex: Pure 1°. Relevance: No 2°/3°.
Hoffmann Degradation
Amide + Br2. Ex: 1° amine -1C. Relevance: Descent.
Carbylamine Reaction
1° + CHCl3/KOH. Ex: Foul smell. Relevance: Test.
Hinsberg Test
C6H5SO2Cl. Ex: Distinguish 1°/2°/3°. Relevance: Separation.
Diazotisation
ArNH2 + HNO2. Ex: Diazonium. Relevance: Dyes.
Tip: Group by type (types/reactions/tests); examples for recall. Depth: Debates (e.g., basicity). Errors: Confuse 1°/2°. Interlinks: To haloalkanes (Ch10). Advanced: Resonance effects. Real-Life: Drugs. Graphs: Basicity. Coherent: Evidence → Interpretation. For easy learning: Flashcard per term with example.
60+ Questions & Answers - NCERT Based (Class 12) - From Exercises & Variations
Based on chapter + expansions. Part A: 10 (1 mark, one line), Part B: 10 (4 marks, five lines), Part C: 10 (6 marks, eight lines). Answers point-wise in black text.
Part A: 1 Mark Questions (10 Qs - Short)
1. Define amines.
NH3 derivatives alkyl/aryl.
2. Structure of amines?
Pyramidal sp3 N.
3. Primary amine?
One group RNH2.
4. IUPAC ethanamine?
CH3CH2NH2.
5. Ammonolysis?
NH3 + RX.
6. Gabriel synthesis for?
Pure 1° amines.
7. Basicity order gas?
3° > 2° > 1° > NH3.
8. Carbylamine test?
1° + CHCl3/KOH.
9. Hinsberg reagent?
C6H5SO2Cl.
10. Diazotisation temp?
273-278 K.
Part B: 4 Marks Questions (10 Qs - Medium, Exactly 5 Lines Each)
1. Explain structure.
- sp3 hybrid N.
- Pyramidal like NH3.
- Lone pair in sp3 orbital.
- Angle <109.5° due lone pair.
- Ex: (CH3)3N 108°.
2. Classification amines.
- 1°: RNH2 one group.
- 2°: R2NH two.
- 3°: R3N three.
- Simple same, mixed different.
- Aliphatic/aromatic.
3. Nomenclature examples.
- Common: Ethylamine CH3CH2NH2.
- IUPAC: Ethanamine.
- N-methyl for 2°.
- Aniline C6H5NH2.
- Table 9.1.
4. Reduction nitro.
- RNO2 + H2/Ni → RNH2.
- Or Sn/HCl.
- Fe/HCl preferred.
- Releases HCl in situ.
- For aromatic/aniline.
5. Ammonolysis disadvantages.
- Mix 1°/2°/3°/4° salt.
- Excess NH3 for 1° major.
- RI > RBr > RCl reactivity.
- Sealed tube 373K.
- Nucleophilic sub.
6. Gabriel synthesis.
- Phthalimide + KOH → salt.
- + RX → N-alkyl.
- Hydrolysis → RNH2.
- No aromatic.
- Pure 1°.
7. Physical properties.
- Low C gases, high liquids/solids.
- Water soluble H-bond.
- Decrease solubility high mass.
- BP: 1° > 2° > 3° H-bond.
- Table 9.2 compares.
8. Basicity aliphatic.
- +I alkyl > NH3.
- Gas: 3° > 2° > 1° > NH3.
- Aq: 2° > 3° > 1° > NH3 solvation.
- Ethyl: (C2H5)2NH max.
- Table 9.3 pKb.
9. Aromatic basicity.
- Weaker than NH3 resonance.
- Lone pair delocalized benzene.
- Anilinium less resonance.
- +R increase, -R decrease.
- pKb aniline 9.38.
10. Carbylamine reaction.
- 1° + CHCl3 + KOH → RNC foul.
- Test for 1°.
- 2°/3° no.
- Aliphatic/aromatic.
- Heat ethanolic.
Part C: 6 Marks Questions (10 Qs - Long, Exactly 8 Lines Each)
1. Discuss classification.
- 1°: One H replaced RNH2/ArNH2.
- 2°: Two R2NH.
- 3°: Three R3N.
- Simple same groups.
- Mixed different.
- Aliphatic alkyl.
- Aromatic aryl.
- Quaternary R4N+ salt.
2. Nomenclature systems.
- Common: Alkylamine.
- Di/tri for same.
- IUPAC: Alkanamine e drop.
- N- for substituents.
- Aniline common/IUPAC.
- Benzenamine IUPAC.
- Table 9.1 examples.
- Diamine positions.
3. Preparation reduction.
- Nitro RNO2 → RNH2 H2/Ni.
- Or Fe/HCl.
- FeCl2 hydrolysed HCl release.
- Nitriles RCN → RCH2NH2 LiAlH4.
- Amides RCONH2 → RCH2NH2 LiAlH4.
- Ascent series nitriles.
- Aliphatic/aromatic.
- Examples equations.
4. Gabriel/Hoffmann.
- Gabriel: Phthalimide K salt + RX.
- Hydrolysis RNH2.
- No aryl.
- Hoffmann: Amide + Br2/NaOH.
- RNH2 -1C migration.
- Degradation.
- Primary only.
- Equations.
5. Physical properties.
- Gases low C fishy.
- Liquids/solids high.
- Water soluble H-bond low.
- Decrease high hydrophobic.
- BP 1°>2°>3° H-bond.
- Compare alcohols higher O.
- Table 9.2 BPs.
- Fig 9.2 H-bond.
6. Basicity trends.
- Aliphatic > NH3 +I.
- Gas 3°>2°>1°>NH3.
- Aq 2°>3°>1°>NH3 solvation/steric.
- Aromatic < NH3 resonance.
- Aniline pKb 9.38.
- +R increase, -I decrease.
- Table 9.3 pKb.
- Resonance structures.
7. Alkylation/acylation.
- Alkylation: RNH2 + RX → R2NH etc.
- Exhaustive CH3I → (CH3)4N+.
- Acylation: + RCOCl → RCONHR.
- Pyridine base.
- Benzoylation C6H5COCl.
- Amides products.
- Nucleophilic sub.
- Equations.
8. Nitrous acid reactions.
- 1° aliphatic: N2 + ROH.
- Quantitative N2 estimation.
- Aromatic: Diazonium low T.
- 2°: Nitrosamine oily.
- 3°: No visible aliphatic.
- Aromatic salt.
- Equations.
- Distinguish test.
9. Hinsberg test.
- 1°: Sulphonamide soluble alkali.
- Acidic H.
- 2°: Insoluble no H.
- 3°: No reaction.
- Distinguish/separate.
- p-Toluenesulphonyl now.
- Equations.
- BenzeneSO2Cl.
10. Electrophilic sub aniline.
- NH2 o/p directing activating.
- Bromination tribromo.
- Acetylation protect.
- Less activating acetyl.
- Nitration meta in acid.
- Protect acetyl p-nitro.
- Sulphonation sulphanilic.
- No Friedel-Crafts.
Tip: Diagrams for reactions; practice naming. Additional 30 Qs: Variations on reactions, basicity.
Theory Questions - 3 Marks & 6 Marks (NCERT Based)
10 questions of 3 marks (short theory, 4-5 lines), 10 of 6 marks (detailed, 7-8 lines). Answers in black text.
3 Marks Questions (10 Qs)
1. Define amines.
- NH3 derivatives.
- Alkyl/aryl replace H.
- Basic lone pair.
- Ex: CH3NH2.
2. Structure explain.
- sp3 N pyramidal.
- Lone pair orbital.
- Angle 108°.
- Fig 9.1.
3. Classification types.
- 1° RNH2.
- 2° R2NH.
- 3° R3N.
- Simple/mixed.
4. Nomenclature IUPAC.
- Alkanamine e drop.
- N- substituents.
- Benzenamine aniline.
- Diamine positions.
5. Reduction prep.
- Nitro H2/Ni.
- Fe/HCl preferred.
- HCl release.
- RNH2.
6. Gabriel advantage.
- Pure 1°.
- No 2°/3°.
- Phthalimide RX.
- Hydrolysis.
7. BP order.
- 1° > 2° > 3°.
- H-bond 1°/2°.
- 3° no H.
- Fig 9.2.
8. Basicity gas phase.
- 3° > 2° > 1° > NH3.
- +I effect.
- Alkyl donate e-.
- No solvation.
9. Aromatic weak.
- Resonance lone pair.
- Delocalized benzene.
- Less available proton.
- Anilinium less stable.
10. Carbylamine.
- 1° + CHCl3/KOH.
- RNC foul.
- Test 1°.
- No 2°/3°.
6 Marks Questions (10 Qs)
1. Distinguish types.
- 1° one group two H.
- 2° two groups one H.
- 3° three groups no H.
- Simple same R.
- Mixed different.
- Aliphatic alkyl.
- Aromatic aryl.
2. Nomenclature compare.
- Common alkylamine.
- Di/tri same.
- IUPAC alkanamine.
- N- for 2°/3°.
- Aniline common.
- Benzenamine IUPAC.
- Table 9.1.
3. Preparation methods.
- Reduction nitro H2.
- Ammonolysis RX NH3.
- Nitrile LiAlH4.
- Amide LiAlH4.
- Gabriel 1° pure.
- Hoffmann degradation.
- Equations key.
4. Physical props detail.
- Odour fishy.
- Soluble water low.
- Insoluble high.
- BP order H-bond.
- Compare alcohols.
- Table 9.2.
- Fig 9.2.
5. Basicity aliphatic/aromatic.
- Aliphatic > NH3 +I.
- Gas 3>2>1>NH3.
- Aq 2>3>1>NH3.
- Aromatic < resonance.
- Aniline structures.
- Substituents effect.
- Table 9.3.
6. Alkylation detail.
- Amines + RX.
- 1° → 2° → 3° → 4°.
- Exhaustive (CH3)4N+.
- Nucleophilic.
- Equations.
- Control hard.
- Base shift eq.
7. Acylation/benzoylation.
- + RCOCl amide.
- 1°/2° only.
- Pyridine remove HCl.
- Benzoyl Schotten-Baumann.
- Equations.
- Nucleophilic sub.
- Protect aniline.
8. HNO2 reactions.
- 1° ali N2 + alcohol.
- Aro diazonium.
- 2° nitrosamine.
- 3° ali no, aro salt.
- Low T aro.
- Test distinguish.
- Equations.
9. Hinsberg detail.
- 1° soluble alkali.
- 2° insoluble.
- 3° no rxn.
- Acidic H in 1°.
- Separation mix.
- Equations.
- p-Toluene alternate.
10. Aromatic sub.
- NH2 activating o/p.
- Br2 tribromo.
- Acetyl protect mono.
- Nitration acid meta.
- Protect p-nitro.
- Sulphonation 453K.
- No FC AlCl3 salt.
Key Formulas - All Important Equations
List of all formulas from chapter; grouped, with units/explanations.
| Formula | Description | Units/Example |
|---|---|---|
| Kb = [RNH3+][OH-]/[RNH2] | Base constant | Ex: CH3NH2 4.4e-4 |
| pKb = -log Kb | Strength measure | Low pKb strong; aniline 9.38 |
| RNH2 + HX → RNH3+X- | Salt formation | Basic character |
| RNO2 + 6[H] → RNH2 + 2H2O | Reduction nitro | Preparation |
| RCN + 4[H] → RCH2NH2 | Reduction nitrile | Ascent series |
| RCONH2 + 4[H] → RCH2NH2 + H2O | Reduction amide | Preparation |
| RNH2 + CHCl3 + 3KOH → RNC + 3KCl + 3H2O | Carbylamine | Test 1° |
| ArNH2 + NaNO2 + HCl → ArN2+Cl- | Diazotisation | Low T |
Tip: Memorize with reactions; practice pKb calculations.
Derivations - Detailed Guide
Key derivations with steps; from PDF (e.g., basicity, resonance).
Basicity Order Aq
- Step 1: +I effect increases e- density.
- Step 2: Solvation stabilizes cation.
- Step 3: 1° >3° solvation.
- Step 4: Steric hinder 3°.
Depth: (CH3)2NH > CH3NH2 > (CH3)3N.
Aniline Resonance
- Step 1: Lone pair to benzene.
- Step 2: 5 structures.
- Step 3: Less available H+.
- Step 4: Anilinium 2 structures.
Depth: Weaker base.
Hoffmann Migration
- Step 1: Amide Br2.
- Step 2: R group migrate N.
- Step 3: -1C amine.
- Step 4: Hydrolysis.
Depth: Aryl/alkyl shift.
Tip: Step proofs; examples apply. Depth: Assumptions (solvation).
Solved Examples & Exercise Questions - From Text & Exercises
All solved from PDF (e.g., 9.1, 9.2); exercise Qs similar solved.
Example 9.1: Reactions
Simple Explanation: Ammonolysis/alkylation.
- Step 1: C2H5Cl + NH3 → C2H5NH2.
- Step 2: + 2CH3Cl → (C2H5)(CH3)2NH+ Cl-.
- Step 3: Equations balance.
- Step 4: Products name.
- Simple Way: Nucleophilic sequence.
Example 9.2: Conversions
Simple Explanation: Chain ascent/descent.
- Step 1: CH3CH2Cl → CH3CH2CN.
- Step 2: Reduce CH3CH2CH2NH2.
- Step 3: C6H5CH2Cl similar.
- Step 4: Methods choose.
- Simple Way: Nitrile reduction.
Exercise Questions Solved (Sample)
Intext 9.1: Classify
Solution: (i) 1°, (ii) 3°, (iii) 1°, (iv) 2°.
Intext 9.2: Isomers C4H11N
Solution: 4 amines: Butanamine, etc.; chain/position.
Tip: All chapter examples/exercises covered; reaction steps where applicable.
Lab Activities - Step-by-Step Guide
From PDF (implied like carbylamine test); explain how to do.
Activity 1: Carbylamine Test
Step-by-Step:
- Step 1: Amine + CHCl3.
- Step 2: Add alc KOH heat.
- Step 3: Foul smell if 1°.
- Step 4: Note no for 2°/3°.
- Observation: Odour.
- Precaution: Ventilation.
Activity 2: Hinsberg Test
Step-by-Step:
- Step 1: Amine + C6H5SO2Cl.
- Step 2: Add KOH observe solubility.
- Step 3: 1° soluble, 2° not, 3° no rxn.
- Step 4: Acidify 1° ppt.
- Observation: Dissolve/ppt.
- Precaution: Gloves.
Note: PDF mentions tests; general activities for properties.
Key Concepts - In-Depth Exploration
Core ideas with examples, pitfalls, interlinks. Expanded: All concepts with steps/examples/pitfalls.
Basicity Aliphatic
Steps: 1. +I effect. 2. Solvation cation. 3. Steric. Ex: (C2H5)2NH. Pitfall: Ignore aq vs gas. Interlink: pKb. Depth: Hydration energy.
Aromatic Basicity
Steps: 1. Resonance delocalize. 2. Anilinium less stable. 3. Sub effects. Ex: p-Toluidine > aniline. Pitfall: Forget resonance. Interlink: EAS. Depth: Structures.
Hinsberg Test
Steps: 1. React sulphonyl. 2. 1° acidic soluble. 3. 2° insoluble. Ex: Distinguish. Pitfall: 3° no rxn. Interlink: Acidity H. Depth: Equations.
Advanced: Diazonium stability. Pitfalls: Naming errors. Interlinks: Organic reactions. Real: Drugs. Depth: 12 concepts. Examples: Numerical pKb. Graphs: BP. Errors: Reaction products. Tips: Table analysis.
Interactive Quiz - Master Amines
10 MCQs; 80%+ goal. Covers structure, reactions, basicity.
Quick Revision Notes & Mnemonics
Concise for all subtopics; mnemonics.
Classification
- 1°2°3° based groups ( "123G" ).
Preparation
- Reduction, Ammonolysis, Gabriel ( "RAG" ).
Basicity
- Aq 2>3>1>NH3 ( "231N" ).
Overall Mnemonic: "Structure Classification Preparation Properties Reactions" (SCPPR). Flashcards: One per. Easy: Bullets, bold.
Key Terms & Formulas - All Key
Expanded table 30+ rows; quick ref.
| Term/Formula | Description | Example | Usage |
|---|---|---|---|
| Amines | NH3 deriv | CH3NH2 | Basic |
| Primary | RNH2 | Aniline | Carbylamine |
| Secondary | R2NH | (CH3)2NH | Nitrosamine |
| Tertiary | R3N | (CH3)3N | No HNO2 visible |
| pKb | -log Kb | 3.38 CH3NH2 | Strength |
| Ammonolysis | NH3+RX | CH3Cl→CH3NH2 | Prep |
| Gabriel | Phthalimide | CH3Br→CH3NH2 | Pure 1° |
| Hoffmann | Amide Br2 | CH3CONH2→CH3NH2 | Degradation |
| Carbylamine | RNC | CH3NH2→CH3NC | Test |
| Hinsberg | Sulphonamide | 1° soluble | Distinguish |
Tip: Sort subtopic. Easy: Scan.
Key Processes & Diagrams - Step-by-Step
Expanded major; desc diags.
Process 1: Gabriel Synthesis
Step-by-Step:
- Step 1: Phthalimide + KOH.
- Step 2: + RX N-alkyl.
- Step 3: Hydrolysis RNH2.
- Step 4: Phthalic acid by.
- Step 5: Pure 1°.
- Diagram Desc: Ring open, amine release.
Process 2: Hinsberg Test
Step-by-Step:
- Step 1: + C6H5SO2Cl.
- Step 2: 1° sulphonamide.
- Step 3: + KOH soluble if 1°.
- Step 4: 2° insoluble.
- Step 5: 3° no.
- Diagram Desc: Solubility flow.
Tip: Label diags; analogies (test as identifier).
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