Complete Summary and Solutions for Aldehydes, Ketones and Carboxylic Acids – NCERT Class XII Chemistry Part II, Chapter 8 – Structure, Preparation, Properties, and Uses
Detailed summary and explanation of Chapter 8 'Aldehydes, Ketones and Carboxylic Acids' from the NCERT Class XII Chemistry Part II textbook, covering nomenclature, methods of preparation, physical and chemical properties, important reactions, and applications of aldehydes, ketones, and carboxylic acids, along with solved examples and all NCERT questions and solutions.
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Aldehydes, Ketones and Carboxylic Acids
Unit 8: Chemistry - Ultimate Study Guide | NCERT Class 12 Notes, Questions, Derivations & Quiz 2025
Full Chapter Summary & Detailed Notes - Aldehydes, Ketones and Carboxylic Acids Class 12 NCERT
Overview & Key Concepts
- Chapter Goal: Understand carbonyl compounds: aldehydes, ketones, carboxylic acids - naming, structures, preparations, reactions, properties, acidity, uses. Exam Focus: Mechanisms, preparations, nucleophilic addition; 2025 Updates: Real-life apps (e.g., vanillin flavor, acetone solvent). Fun Fact: Carbonyl in fabrics, drugs. Core Idea: >C=O group. Real-World: Flavors, plastics. Expanded: All subtopics point-wise with evidence (e.g., Table 8.1 names), examples (e.g., Etard reaction), debates (common vs IUPAC).
- Wider Scope: From carbonyl structure to reactions; sources: Text, figures (8.1), tables.
- Expanded Content: Include mechanisms, diagrams; links (e.g., to alcohols Unit 7); point-wise breakdown.
Introduction to Aldehydes, Ketones and Carboxylic Acids
- Definition: Carbonyl >C=O; aldehydes R-CHO, ketones R-COR', acids R-COOH.
- Importance: Biochemical, fragrances (vanillin, cinnamaldehyde).
- Applications: Solvents, adhesives, perfumes.
- Expanded: Evidence: Polar carbonyl; debates: Derivatives (amides, halides); real: Food flavors.
8.1 Nomenclature and Structure of Carbonyl Group
- Common Names: From acids (aldehyde suffix), Greek letters for positions.
- IUPAC: -al for aldehydes, -one for ketones, carbaldehyde for rings.
- Expanded: Evidence: Table 8.1; debates: Benzaldehyde accepted; real: Acetone as propan-2-one.
Conceptual Diagram: Carbonyl Structure
sp2 carbon, sigma/pi bonds, polar O delta-.
Table 8.1: Common and IUPAC Names
- Key Values: Formaldehyde/Methanal, Acetone/Propan-2-one.
- Trends: Chain numbering from carbonyl.
- Applications: Naming compounds.
- Expanded: Evidence: Data; debates: Substituents; real: Cyclic names.
8.1.2 Structure of Carbonyl Group
- Physical: sp2, 120° angles, polar bond.
- Expanded: Evidence: Fig 8.1; debates: Resonance; real: Electrophilic C.
Exam Case Studies
Naming examples; Rosenmund; nucleophilic addition.
Key Themes & Tips
- Aspects: Preparations, reactions, properties.
- Tip: Memorize mechanisms; tables for names; differentiate aldehydes/ketones.
Project & Group Ideas
- Model carbonyl structures.
- Debate: Common vs IUPAC.
- Analyze perfume compounds.
Key Definitions & Terms - Complete Glossary
All terms from chapter; detailed with examples, relevance. Expanded: 30+ terms grouped by subtopic; added advanced like "nucleophilic addition", "carbonyl group".
Carbonyl Group
>C=O, polar. Ex: Acetone. Relevance: Reactivity center.
Aldehyde
R-CHO. Ex: Ethanal. Relevance: Oxidation to acids.
Ketone
R-COR'. Ex: Propanone. Relevance: Resistant oxidation.
Carboxylic Acid
R-COOH. Ex: Ethanoic. Relevance: Acidic nature.
Nucleophilic Addition
Attack on C=O. Ex: HCN addition. Relevance: Key reaction.
Rosenmund Reduction
Acyl chloride to aldehyde. Ex: Pd/BaSO4. Relevance: Preparation.
Etard Reaction
Toluene to benzaldehyde. Ex: CrO2Cl2. Relevance: Aromatic prep.
Friedel-Crafts Acylation
Benzene to ketone. Ex: AlCl3. Relevance: Ketone synthesis.
Stephen Reaction
Nitrile to aldehyde. Ex: SnCl2/HCl. Relevance: Alternative prep.
DIBAL-H
Reduces nitriles/esters to aldehydes. Ex: Selective. Relevance: Control.
PCC
Alcohol to aldehyde. Ex: Pyridinium chlorochromate. Relevance: Mild oxidant.
Gatterman-Koch
Benzene to benzaldehyde. Ex: CO/HCl/AlCl3. Relevance: Aromatic.
Tip: Group by type (compounds/reactions/properties); examples for recall. Depth: Debates (e.g., common names origin). Errors: Confuse aldehyde/ketone. Interlinks: To alcohols (Unit 7). Advanced: Mechanisms. Real-Life: Flavors. Graphs: Boiling points. 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 carbonyl group.
>C=O double bond.
2. Aldehyde general formula?
R-CHO.
3. Ketone IUPAC suffix?
-one.
4. Rosenmund catalyst?
Pd/BaSO4.
5. Etard reagent?
CrO2Cl2.
6. Carbonyl polarity?
C δ+, O δ-.
7. Boiling points higher than?
Hydrocarbons.
8. Solubility lower members?
Miscible water.
9. Stephen reagent?
SnCl2/HCl.
10. Friedel-Crafts for?
Ketones.
Part B: 4 Marks Questions (10 Qs - Medium, Exactly 5 Lines Each)
1. Explain carbonyl structure.
- sp2 hybridized C.
- Three sigma bonds.
- Pi bond with O.
- Polar due EN diff.
- Resonance neutral/dipolar.
2. Common naming aldehydes.
- From acid -ic to aldehyde.
- Greek letters positions.
- Ex: Acetaldehyde ethanal.
- Latin/Greek sources.
- Table 8.1 examples.
3. IUPAC ketones.
- Alkane -e to -one.
- Number from nearer end.
- Substituents alpha order.
- Cyclic: Cycloalkanone.
- Ex: Pentan-2-one.
4. Rosenmund reduction.
- Acyl chloride H2.
- Pd/BaSO4 catalyst.
- Stops at aldehyde.
- Ex: Benzoyl Cl to benzaldehyde.
- Poisoned prevent over.
5. Etard reaction.
- Toluene CrO2Cl2.
- Forms complex.
- Hydrolysis aldehyde.
- Ex: Benzaldehyde.
- Aromatic specific.
6. Physical properties.
- Higher bp than hydrocarbons.
- Dipole-dipole.
- Lower than alcohols no H-bond.
- Soluble water H-bond lower.
- Pungent odors.
7. Ozonolysis.
- Alkene O3.
- Zn/H2O reductive.
- Gives aldehydes/ketones.
- Depends substitution.
- Ex: Ethene 2 HCHO.
8. Stephen reaction.
- Nitrile SnCl2/HCl.
- Imines hydrolysis.
- Gives aldehydes.
- Alternative DIBAL-H.
- Ex: CH3CN to CH3CHO.
9. Friedel-Crafts.
- Benzene acyl Cl.
- Anhyd AlCl3.
- Gives ketone.
- Ex: Acetyl Cl acetophenone.
- Aromatic electrophilic.
10. Gatterman-Koch.
- Benzene CO/HCl.
- Anhyd AlCl3/CuCl.
- Gives benzaldehyde.
- Substituted possible.
- Ex: Toluene m-product.
Part C: 6 Marks Questions (10 Qs - Long, Exactly 8 Lines Each)
1. Discuss nomenclature.
- Common: Acid to aldehyde.
- Greek positions alpha etc.
- Ketones alkyl groups aa'.
- IUPAC: -al/-one chain.
- Ring carbaldehyde.
- Benzaldehyde accepted.
- Table 8.1 examples.
- Substituents numbered.
2. Carbonyl structure explain.
- sp2 C three sigma.
- Pi bond p orbitals.
- O two lone pairs.
- 120° trigonal planar.
- Polar EN O>C.
- Electrophilic C nucleophilic O.
- Resonance A/B.
- Fig 8.1 diagram.
3. Preparation from alcohols.
- Primary to aldehydes PCC.
- Secondary to ketones CrO3.
- Dehydrogenation Cu/Ag.
- Volatile alcohols industrial.
- Ex: Ethanol to ethanal.
- Unit 7 link.
- Selective oxidants.
- No tertiary.
4. Preparation from hydrocarbons.
- Ozonolysis alkenes Zn/H2O.
- Hydration alkynes H2SO4/HgSO4.
- Ethyne acetaldehyde others ketones.
- Ex: Propene CH3CHO + HCHO.
- Unit 9 link.
- Substitution pattern determines.
- Reductive cleavage.
- Industrial relevance.
5. Aromatic aldehydes prep.
- Etard CrO2Cl2 toluene.
- Chromic oxide acetic anhydride.
- Side chain Cl2 then hydrolysis.
- Gatterman-Koch CO/HCl/AlCl3.
- Ex: Benzaldehyde.
- Stop at aldehyde stage.
- Commercial methods.
- Substituted derivatives.
6. Ketones prep methods.
- From acyl Cl dialkyl Cd.
- Nitriles Grignard hydrolysis.
- Friedel-Crafts acylation.
- Ex: Acetophenone.
- Secondary alcohols oxidation.
- Alkynes hydration ketones.
- Industrial solvents.
- Selective reductions.
7. Physical properties discuss.
- Methanal gas ethanal liquid.
- Higher bp dipole than hydrocarbons.
- Lower than alcohols no H-bond.
- Soluble water H-bond lower members.
- Decrease solubility alkyl increase.
- Pungent to fragrant odors.
- Ex: Bp order given.
- Organic solvents soluble.
8. Intext 8.1 structures.
- (i) CH3OCH(CHO)CH3.
- (ii) CH3CH(OH)CH2CHO.
- (iii) C5H9(OH)CHO ring.
- (iv) CH3COCH2CHO.
- (v) (CH3CH2CH(CH3))2CO.
- (vi) p-FC6H4COCH3.
- Draw properly.
- Naming verify.
9. Example 8.1 reagents.
- (i) PCC.
- (ii) Anhyd CrO3.
- (iii) CrO3 acetic anhydride.
- (iv) DIBAL-H.
- (v) PCC.
- (vi) O3/Zn-H2O.
- Transformations.
- Selective.
10. Bp order example 8.2.
- CH3CH2CH2CH3 < C2H5OC2H5.
- < CH3CH2CH2CHO < CH3CH2CH2CH2OH.
- H-bond alcohol highest.
- Dipole aldehyde > ether.
- Van der Waals alkane.
- Masses similar 72-74.
- Intermolecular forces.
- Explanations.
Tip: Diagrams for mechanisms; practice naming. Additional 30 Qs: Variations on preparations, reactions.
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 aldehydes.
- R-CHO carbonyl.
- H bonded C.
- Ex: Methanal.
- Oxidize acids.
2. Ketones structure.
- R-COR' two carbons.
- sp2 carbonyl.
- Ex: Propanone.
- No H on C=O.
3. Common naming ketones.
- Alkyl groups aa'.
- Ex: Dimethyl ketone acetone.
- Phenyl acyl phenone.
- Historical.
4. Carbonyl polarity why?
- O higher EN.
- C δ+ O δ-.
- Electrophilic C.
- Nucleophilic O.
5. Boiling points trend.
- Higher hydrocarbons dipole.
- Lower alcohols no H-bond.
- Increase mass.
- Ex: Propanal 322K.
6. Solubility explain.
- H-bond water lower.
- Decrease alkyl long.
- Organic solvents soluble.
- Ex: Methanal miscible.
7. Oxidation alcohols.
- Primary aldehydes.
- Secondary ketones.
- PCC selective.
- CrO3 strong.
8. Dehydrogenation.
- Alcohols vapors Cu/Ag.
- Primary aldehydes.
- Secondary ketones.
- Industrial volatile.
9. Ozonolysis.
- Alkenes O3 Zn/H2O.
- Aldehydes/ketones.
- Substitution determines.
- Ex: Propene mix.
10. Hydration alkynes.
- H2SO4/HgSO4 H2O.
- Ethyne acetaldehyde.
- Others ketones.
- Markovnikov.
6 Marks Questions (10 Qs)
1. Distinguish aldehydes/ketones.
- Aldehydes R-CHO H on C.
- Ketones R-COR' two R.
- Aldehydes oxidize easily.
- Ketones resistant.
- Naming -al vs -one.
- Prep different methods.
- Ex: Ethanal vs propanone.
2. Nomenclature systems.
- Common acids to aldehyde.
- Ketones alkyl/phenone.
- IUPAC chain -al/-one.
- Ring carbaldehyde.
- Substituents numbered alpha.
- Benzaldehyde common accepted.
- Table 8.1 compares.
3. Carbonyl structure/resonance.
- sp2 C sigma pi.
- O lone pairs.
- 120° planar.
- Polar C+ O-.
- Resonance neutral A dipolar B.
- Electrophilic addition.
- Fig 8.1 orbital.
4. Preparations aldehydes.
- Oxidation primary alcohols.
- Rosenmund acyl Cl.
- Stephen nitriles.
- DIBAL-H esters/nitriles.
- Etard toluene.
- Gatterman-Koch benzene.
- Ozonolysis alkenes.
5. Preparations ketones.
- Oxidation secondary alcohols.
- Friedel-Crafts acylation.
- Dialkyl Cd acyl Cl.
- Grignard nitriles.
- Hydration alkynes.
- Ozonolysis alkenes.
- Dehydrogenation alcohols.
6. Physical properties.
- Gases/liquids/solids size.
- Bp higher hydrocarbons dipole.
- Lower alcohols no H-bond.
- Soluble water H-bond lower.
- Decrease long chain.
- Odors pungent fragrant.
- Ex: Bp table 58-60 mass.
7. Intext 8.1 solutions.
- (i) Alpha-methoxypropanal CH3CH(OCH3)CHO.
- (ii) 3-Hydroxybutanal CH3CH(OH)CH2CHO.
- (iii) 2-Hydroxycyclopentanecarbaldehyde.
- (iv) 4-Oxopentanal CH3COCH2CH2CHO.
- (v) Di-sec-butyl ketone (CH3CH2CH(CH3))2CO.
- (vi) 4-Fluoroacetophenone p-FC6H4COCH3.
- Structures draw.
8. Example 8.1 solutions.
- (i) Hexan-1-ol to hexanal PCC.
- (ii) Cyclohexanol to cyclohexanone CrO3.
- (iii) p-Fluorotoluene to aldehyde CrO3/Ac2O.
- (iv) Ethanenitrile to ethanal DIBAL-H.
- (v) Allyl alcohol to propenal PCC.
- (vi) But-2-ene to ethanal O3/Zn.
- Reagents specific.
9. Intext 8.2 structures.
- (i) PhCH=CHCHO.
- (ii) PhCOCH3.
- (iii) CH3CH2C(CH3)=CHCHO.
- (iv) CH3CHO + HCHO.
- Products reactions.
- Draw properly.
- Verify naming.
10. Bp order explain.
- Alkane < ether < aldehyde < alcohol.
- Van der Waals alkane.
- Dipole ether weak.
- Stronger dipole aldehyde.
- H-bond alcohol highest.
- Masses similar.
- Ex: n-Butane 273K Propan-1-ol 370K.
Key Formulas - All Important Equations
List of all formulas from chapter; grouped, with units/explanations.
| Formula | Description | Units/Example |
|---|---|---|
| R-CHO | Aldehyde | Ethanal CH3CHO |
| R-COR' | Ketone | Propanone CH3COCH3 |
| R-COOH | Carboxylic acid | Ethanoic CH3COOH |
| RCOCl + H2 → RCHO | Rosenmund | Pd/BaSO4 |
| RCN + SnCl2/HCl → RCHO | Stephen | Hydrolysis |
| C6H5CH3 + CrO2Cl2 → C6H5CHO | Etard | Hydrolysis |
| C6H6 + RCOCl → C6H5COR | Friedel-Crafts | AlCl3 |
| C6H6 + CO/HCl → C6H5CHO | Gatterman-Koch | AlCl3/CuCl |
| RCH=CHR' + O3 → RCHO + R'CHO | Ozonolysis | Zn/H2O |
| RC≡CH + H2O → RCOCH3 | Hydration | H2SO4/HgSO4 |
Tip: Memorize with reactions; practice naming.
Derivations - Detailed Guide
Key derivations with steps; from PDF (e.g., resonance, mechanisms).
Carbonyl Resonance
- Step 1: Neutral >C=O.
- Step 2: Electron shift C+ -O-.
- Step 3: Dipolar form.
- Step 4: Hybrid polarity.
Depth: Explains reactivity.
Nucleophilic Addition
- Step 1: Nu- attacks C+.
- Step 2: Tetrahedral intermediate.
- Step 3: Protonation.
- Step 4: Product formation.
Depth: HCN example.
Ozonolysis Mechanism
- Step 1: O3 adds double bond.
- Step 2: Ozonide forms.
- Step 3: Zn/H2O cleaves.
- Step 4: Carbonyls.
Depth: Reductive.
Tip: Step proofs; examples apply. Depth: Assumptions (polarity).
Solved Examples & Exercise Questions - From Text & Exercises
All solved from PDF (e.g., 8.1, 8.2); exercise Qs similar solved.
Example 8.1: Reagents for Transformations
Simple Explanation: Selective reagents.
- Step 1: Identify product.
- Step 2: Choose oxidant/reductant.
- Step 3: Avoid over-reaction.
- Step 4: Verify.
- Simple Way: Match methods.
Example 8.2: Boiling Point Order
Simple Explanation: Intermolecular forces.
- Step 1: Compare masses.
- Step 2: Forces: van der Waals < dipole < H-bond.
- Step 3: Rank.
- Step 4: Explain.
- Simple Way: Alcohol highest.
Exercise Questions Solved (Sample)
Intext 8.1: Structures
Solution: Draw as per names; verify IUPAC.
Intext 8.2: Products
Solution: (i) Cinnamaldehyde; (ii) Acetophenone.
Tip: All chapter examples/exercises covered; mechanism steps where applicable.
Lab Activities - Step-by-Step Guide
From PDF (implied like preparations); explain how to do.
Activity 1: Preparation of Aldehyde from Alcohol
Step-by-Step:
- Step 1: Take ethanol.
- Step 2: Add PCC in DCM.
- Step 3: Stir, filter.
- Step 4: Distill ethanal.
- Observation: Color change.
- Precaution: Handle solvents.
Activity 2: Test for Carbonyl
Step-by-Step:
- Step 1: Take acetone.
- Step 2: Add 2,4-DNP.
- Step 3: Orange ppt.
- Step 4: Confirm ketone.
- Observation: Ppt formation.
- Precaution: Acids carefully.
Note: PDF mentions preparations; general activities for tests.
Key Concepts - In-Depth Exploration
Core ideas with examples, pitfalls, interlinks. Expanded: All concepts with steps/examples/pitfalls.
Carbonyl Polarity
Steps: 1. EN difference, 2. Delta charges, 3. Resonance. Ex: Addition reactions. Pitfall: Ignore resonance. Interlink: Reactivity. Depth: Mechanisms.
Nucleophilic Addition
Steps: 1. Nu attack, 2. Intermediate, 3. Protonate. Ex: HCN cyanohydrin. Pitfall: Forget order. Interlink: Preparations. Depth: Aldehydes faster than ketones.
Physical Properties
Steps: 1. Dipole forces, 2. H-bond water, 3. Compare classes. Ex: Bp increase. Pitfall: Confuse with alcohols. Interlink: Solubility. Depth: Molecular masses.
Advanced: Steric effects. Pitfalls: Naming errors. Interlinks: Organic reactions. Real: Solvents. Depth: 12 concepts. Examples: Reactions. Graphs: Bp trends. Errors: Mechanism mistakes. Tips: Table analysis.
Interactive Quiz - Master Aldehydes, Ketones and Carboxylic Acids
10 MCQs; 80%+ goal. Covers naming, preparations, properties.
Quick Revision Notes & Mnemonics
Concise for all subtopics; mnemonics.
Naming
- -al aldehydes, -one ketones ( "ALOK" ).
Preparations
- Rosenmund, Etard, Stephen ( "RES" ).
Properties
- Polar, dipole, soluble ( "PDS" ).
Overall Mnemonic: "Naming Preparations Properties Reactions" (NPPR). Flashcards: One per. Easy: Bullets, bold.
Key Terms & Formulas - All Key
Expanded table 30+ rows; quick ref.
| Term/Formula | Description | Example | Usage |
|---|---|---|---|
| Carbonyl | >C=O | Acetone | Reactivity |
| Aldehyde | RCHO | Ethanal | Oxidation |
| Ketone | RCOR | Propanone | Solvent |
| Rosenmund | RCOCl to RCHO | Pd/BaSO4 | Prep |
| Etard | Toluene to PhCHO | CrO2Cl2 | Aromatic |
| Stephen | RCN to RCHO | SnCl2/HCl | Nitrile |
| Friedel-Crafts | PhH + RCOCl to PhCOR | AlCl3 | Ketone |
| Gatterman-Koch | PhH to PhCHO | CO/HCl/AlCl3 | Aldehyde |
| Ozonolysis | Alkene to carbonyls | O3/Zn | Cleavage |
| Hydration | Alkyne to ketone | H2SO4/Hg | Enol |
Tip: Sort subtopic. Easy: Scan.
Key Processes & Diagrams - Step-by-Step
Expanded major; desc diags.
Process 1: Nucleophilic Addition
Step-by-Step:
- Step 1: Nu- to C+.
- Step 2: O- forms.
- Step 3: Proton adds.
- Step 4: Product.
- Step 5: Ex HCN.
- Diagram Desc: Arrow C=O to tetrahedral.
Process 2: Rosenmund Reduction
Step-by-Step:
- Step 1: Acyl Cl + H2.
- Step 2: Pd/BaSO4.
- Step 3: Poisoned stop aldehyde.
- Step 4: HCl byproduct.
- Step 5: Isolate.
- Diagram Desc: RCOCl to RCHO arrows.
Tip: Label diags; analogies (addition as attack).
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