Chapter-Wise Detailed Analysis of CBSE Class 12 Organic Chemistry Board Exam Questions (Based on PYQs 2020-2025)

Building on the previous overview, this provides a more detailed chapter-wise breakdown for Organic Chemistry in CBSE Class 12 (Units 10-15 from NCERT). The analysis is derived from trends in previous year question papers (PYQs) from 2020-2025, including the 2025 paper which was rated easy to moderate overall, with organic sections being straightforward and NCERT-based. Organic Chemistry typically carries 28-33 marks (40-45% of the paper), with a focus on application, mechanisms, and conversions. Questions are spread across MCQs (1 mark), very short answers (VSA, 2 marks), short answers (SA, 3 marks), case-based (4 marks), and long answers (LA, 5 marks).

Repetition is high for core concepts (e.g., mechanisms appear in 5-6/6 years). Difficulty in 2025 was easy for organic (per student feedback from analyses), with no out-of-syllabus questions. Trends show increased case-based questions post-2022, emphasizing real-life applications (e.g., drug synthesis). For 2025, organic was ~33 marks, direct from NCERT, with predictable reactions like Aldol and Cannizzaro.

Unit 10: Haloalkanes and Haloarenes (4-6 Marks Total, High Repetition: 5/6 Years)

Subtopics Covered

Nomenclature, isomerism (optical, positional), preparation (from alcohols, alkenes, hydrocarbons), reactions (SN1/SN2, E1/E2, nucleophilic substitution, elimination, reactions with metals like Wurtz), aryl halides (low reactivity, Friedel-Crafts failure), polyhalogen compounds (e.g., chloroform, iodoform), environmental impact (CFCs).

Marks Distribution and Question Types

• 1 mark: MCQs on reactivity orders or distinction (e.g., SN1 vs SN2 factors).
• 2-3 marks: Reasoning or short mechanisms (e.g., why aryl halides don't undergo SN2).
• 5 marks: Conversions or full mechanism (e.g., multi-step synthesis like alkyl halide to alcohol).

Repetition Frequency

High; SN mechanisms and chirality repeat annually. In 2025, 6 marks (per analysis), with easy MCQs and SA on substitution.

Named Reactions

Finkelstein, Swarts, Wurtz, Wurtz-Fittig, Sandmeyer (for aryl), Friedel-Crafts (failure in aryl halides). These appear in 4-5/6 years, often as 3-mark equations.

Reasoning-Type Questions

Common (80% papers); e.g., "Why is the boiling point of chloroethane higher than ethane?" (dipole-dipole); "Why do tertiary halides favor SN1?" (carbocation stability). Repetition: 5/6 years.

Mechanisms Asked

SN1 (carbocation intermediate, racemization), SN2 (backside attack, inversion), E1/E2 (base strength, Saytzeff rule). Detailed steps with arrows required in 3-5 mark questions; repeated in 5/6 years, e.g., 2023-2025 SN1 for tert-butyl chloride.

Most Important Questions (from Analysis)

1. Explain the mechanism of SN1 reaction with an example (3 marks, repeated 2021, 2023, 2025).
2. Convert chlorobenzene to phenol (5 marks, multi-step, repeated 2020, 2022, 2024).
3. Distinguish between SN1 and SN2 (2 marks, reasoning, annual repeat).
4. Why are vinyl halides unreactive in nucleophilic substitution? (2 marks, 2022, 2024).
5. Case-based: Environmental impact of DDT (4 marks, 2024-2025).

Unit 11: Alcohols, Phenols and Ethers (4-6 Marks Total, High Repetition: 5/6 Years)

Subtopics Covered

Classification (1°/2°/3° alcohols), nomenclature, preparation (hydration of alkenes, reduction of carbonyls, Grignard), reactions (dehydration to alkenes/ethers, oxidation, esterification, acidic nature of phenols, electrophilic substitution in phenols), ethers (Williamson synthesis, cleavage by HI), tests (Lucas, iodoform, ferric chloride for phenols).

Marks Distribution and Question Types

• 1 mark: MCQs on acidity/basicity orders.
• 2 marks: VSA reasoning (e.g., phenol acidity vs alcohol).
• 3 marks: Mechanisms or equations.
• 5 marks: Conversion chains or case-based (e.g., industrial uses).

Repetition Frequency

High; dehydration and Williamson repeat often. In 2025, 6 marks, straightforward per feedback.

Named Reactions

Williamson ether synthesis, Reimer-Tiemann (phenols to salicylaldehyde), Kolbe's (phenols to salicylic acid). Appear in 5/6 years, as 3-mark with conditions.

Reasoning-Type Questions

Frequent (90% papers); e.g., "Why are phenols more acidic than alcohols?" (resonance stabilization of phenoxide); "Why do ethers have lower boiling points?" (no H-bonding). Repeated 6/6 years.

Mechanisms Asked

Dehydration (E1 for 2°/3°, carbocation rearrangement), HI cleavage of ethers (SN2 for methyl, SN1 for tertiary), Reimer-Tiemann (carbene intermediate). Arrow-pushing required; repeated in 4-5/6 years, e.g., 2020-2025 dehydration.

Most Important Questions

1. Write the mechanism for acid-catalyzed dehydration of ethanol (3 marks, repeated 2021-2025).
2. Convert phenol to aspirin (5 marks, Kolbe + esterification, 2020, 2023).
3. Explain why ortho-nitrophenol is steam volatile but para is not (2 marks, H-bonding, annual).
4. Distinguish alcohols using Lucas test (2 marks, 2022, 2024-2025).
5. Case-based: Synthesis of aspirin (4 marks, 2023-2025).

Unit 12: Aldehydes, Ketones and Carboxylic Acids (6-8 Marks Total, Very High Repetition: 6/6 Years)

Subtopics Covered

Nomenclature, preparation (oxidation, ozonolysis, Friedel-Crafts acylation), reactions (nucleophilic addition: HCN, NH3 derivatives; aldol/cross-aldol, Cannizzaro, oxidation/reduction), carboxylic acids (acidity, esterification, decarboxylation, HVZ), tests (Tollens', Fehling's, iodoform).

Marks Distribution and Question Types

• 1-2 marks: MCQs on tests or reactivity.
• 3 marks: Mechanisms (e.g., aldol).
• 5 marks: Conversions (e.g., A to B to C) or case-based.

Repetition Frequency

Highest; aldol and iodoform in every paper. In 2025, 8 marks, easy with named reactions like Aldol/Cannizzaro.

Named Reactions

Aldol condensation, Cannizzaro, Clemmensen, Wolff-Kishner, HVZ, Rosenmund, Etard, Haloform. Core repeats (6/6 years), often 3-5 marks with equations/mechanisms.

Reasoning-Type Questions

Common; e.g., "Why do aldehydes reduce Tollens' but ketones don't?" (alpha-H absence); "Why are carboxylic acids stronger than phenols?" (resonance). 6/6 years.

Mechanisms Asked

Nucleophilic addition (e.g., cyanohydrin), aldol (enolate attack), Cannizzaro (hydride transfer), HVZ (enol form). Detailed with intermediates; repeated annually, e.g., 2025 aldol.

Most Important Questions

1. Write mechanism for Cannizzaro reaction on benzaldehyde (3 marks, repeated 2020-2025).
2. Convert ethanal to 3-hydroxybutanal (aldol, 3 marks, annual).
3. Distinguish aldehyde/ketone using tests (2 marks, 6/6 years).
4. Explain acidity order: carboxylic acid > phenol > alcohol (2 marks, 2021-2025).
5. Case-based: Iodoform test for alcohols/ketones (4 marks, 2022-2025).

Unit 13: Amines (3-5 Marks Total, Medium Repetition: 4/6 Years)

Subtopics Covered

Classification (1°/2°/3°), preparation (reduction of nitro, Gabriel, Hoffmann), basicity (aliphatic > aromatic), reactions (alkylation, acylation, carbylamine, diazotization, coupling), tests (Hinsberg, carbylamine).

Marks Distribution and Question Types

• 1 mark: MCQs on basicity.
• 2-3 marks: Reasoning or distinctions.
• 5 marks: Synthesis chains.

Repetition Frequency

Medium; basicity and Hinsberg repeat. In 2025, 6 marks, NCERT-based.

Named Reactions

Gabriel phthalimide, Hoffmann bromamide, Sandmeyer (from diazonium), Azo coupling. 4/6 years, as 3-mark.

Reasoning-Type Questions

High; e.g., "Basicity order: 2° > 1° > 3° amines" (solvation, inductive); "Why aniline less basic?" (resonance). 5/6 years.

Mechanisms Asked

Diazotization (N2+ formation), Hinsberg (sulfonamide solubility). Less detailed, but repeated 4/6 years.

Most Important Questions

1. Arrange basicity: CH3NH2, (CH3)2NH, C6H5NH2 (2 marks, repeated 2020-2025).
2. Convert nitrobenzene to aniline to diazonium (5 marks, 2021, 2023-2025).
3. Distinguish 1°/2°/3° amines via Hinsberg (3 marks, 4/6 years).
4. Why can't aliphatic amines be prepared by Gabriel? (2 marks, 2022, 2024).
5. Case-based: Dye synthesis via coupling (4 marks, 2023-2025).

Unit 14: Biomolecules (3-4 Marks Total, Medium Repetition: 4/6 Years)

Subtopics Covered

Carbohydrates (mono/di/poly, glucose structure, mutarotation, glycosidic linkages), proteins (primary/secondary/tertiary/quaternary, denaturation), enzymes (catalysis), vitamins (deficiencies), nucleic acids (DNA/RNA structure).

Marks Distribution and Question Types

• 1-2 marks: MCQs on structures.
• 3 marks: Reasoning (e.g., reducing sugars).

Repetition Frequency

Medium; glucose and proteins repeat. In 2025, 7 marks (including polymers?), easy.

Named Reactions

None major, but linkage formations (e.g., peptide, glycosidic).

Reasoning-Type Questions

Common; e.g., "Why is sucrose non-reducing?" (no free carbonyl); "Denaturation of proteins" (H-bond breaking). 4/6 years.

Mechanisms Asked

Rare; mutarotation (ring opening/closing) in 3/6 years.

Most Important Questions

1. Draw glucose pyranose form; explain mutarotation (3 marks, repeated 2020-2024).
2. Structure levels of proteins (3 marks, 4/6 years).
3. Why vitamin C can't be stored? (2 marks, 2022-2025).
4. Distinguish DNA/RNA (2 marks, 2021, 2023).
5. Case-based: Enzyme action in digestion (4 marks, 2024-2025).

Unit 15: Polymers (2-3 Marks Total, Low Repetition: 3/6 Years)

Subtopics Covered

Classification (addition/condensation, natural/synthetic), preparation (e.g., nylon-6,6, bakelite, PVC), biodegradable polymers (PHA, starch-based).

Marks Distribution and Question Types

• 1-2 marks: MCQs on types/examples.
• 3 marks: Preparation or properties.

Repetition Frequency

Low; nylon and biodegradable repeat occasionally. In 2025, possibly bundled with biomolecules (0-3 marks).

Named Reactions

Condensation polymerizations (e.g., nylon from hexamethylenediamine/adipic acid).

Reasoning-Type Questions

"Difference between thermosetting/thermoplastic" (cross-linking); "Why biodegradable polymers?" (environmental). 3/6 years.

Mechanisms Asked

Polymerization steps (free radical for addition, condensation for others); rare, 2/6 years.

Most Important Questions

1. Prepare nylon-6,6 with equation (3 marks, repeated 2020, 2023, 2025).
2. Classify polymers: addition vs condensation (2 marks, 2021-2024).
3. Examples of biodegradable polymers (2 marks, 2022-2025).
4. Distinguish natural/synthetic rubber (2 marks, 2020, 2024).
5. Case-based: Plastic pollution (4 marks, 2023-2025).

Overall Insights for 2026 Prep

Focus on NCERT for 80% coverage; practice mechanisms with diagrams and conversions. High-repetition areas (aldol, SN, basicity) can fetch 15+ marks. Use PYQs from 2020-2025 for patterns—organic was easier in 2025 than 2023 (more twisted). Student feedback: Thorough NCERT study ensures full marks in organic.