ISC Chemistry 2026: Complete Class 11 & 12 Guide – Reactions, Mechanisms, Notes & Syllabus

 ISC Chemistry 2026 – Complete Guide for Class 11 & 12 (Theory + All Reactions + Mechanisms)

Chemistry in ISC Class 11 & 12 forms the core foundation for competitive exams like JEE, NEET, IISER, and for higher studies in science. The ISC curriculum focuses on conceptual depth, problem-solving, reaction mechanisms, and application-based questions.

This guide covers:

• Full ISC Chemistry 2026 syllabus

• Detailed topic explanations

• All possible organic reactions

• Reaction mechanisms (SN1, SN2, E1, E2, electrophilic substitution, nucleophilic addition, etc.)

• Named reactions

• Physical chemistry formulae

• Inorganic chemistry principles and trends

• ISC exam writing format + diagrams

• Practical chemistry principles

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⭐ PART A: CLASS 11 ISC CHEMISTRY 2026 – COMPLETE THEORY

1. Some Basic Concepts of Chemistry

• Mole concept

• Empirical and molecular formula

• Stoichiometry

• Limiting reagent

• Percentage composition

• Significant figures

• Laws of chemical combination

Important relationship:
Moles = Mass / Molar Mass
Molarity = Moles of solute / Volume (L)

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2. Structure of Atom

• Discovery of electron, proton, neutron

• Thomson model

• Rutherford model

• Bohr’s quantization

• Quantum numbers (n, l, m, s)

• Shapes of orbitals (s, p, d)

• Hund’s rule, Pauli principle

• Electronic configuration

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3. Classification of Elements & Periodicity

• Modern periodic law

• Trends in atomic radius, ionic radius, IE, EA, EN

• d-block contraction & f-block contraction

• Diagonal relationship (Li-Mg, Be-Al)

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4. Chemical Bonding & Molecular Structure

• Types: Ionic, covalent, coordinate

• VSEPR theory

• Hybridisation (sp, sp2, sp3, sp3d, sp3d2)

• MO theory (bond order, paramagnetism)

• Hydrogen bonding

Important bond order relation:
Bond Order = (Nb – Na)/2

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5. States of Matter

Gaseous State

• Ideal gas equation: PV = nRT

• Dalton’s law

• Graham’s law

• Kinetic theory

Liquid State

• Surface tension

• Viscosity

• Vapour pressure

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6. Thermodynamics

• First law

• Internal energy

• Enthalpy

• Hess law

• Second law, entropy

• Gibbs free energy

• Spontaneity: ΔG < 0

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7. Equilibrium

Chemical Equilibrium

• Law of mass action

• Le Chatelier’s principle

• Kc, Kp relationships

Ionic Equilibrium

• pH, pOH

• Ka, Kb

• Hydrolysis

• Buffer solutions

• Solubility product (Ksp)

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8. Redox Reactions

• Oxidation number

• Redox balancing (ion-electron method)

• Disproportionation

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9. Organic Chemistry – Basic Principles

• Electron displacement: Inductive, resonance, hyperconjugation

• Types of reagents: electrophiles, nucleophiles

• Types of reactions:

  • Substitution (SN1, SN2)

  • Elimination (E1, E2)

  • Addition (electrophilic, nucleophilic)

  • Rearrangement

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10. Hydrocarbons

Alkanes

Reactions:

1. Halogenation (Free radical mechanism)

   • Initiation: Cl₂ → 2Cl•

   • Propagation: Cl• + CH₄ → CH₃• + HCl

   • Termination: CH₃• + CH₃• → C₂H₆

2. Combustion

3. Isomerisation

4. Cracking

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Alkenes

Electrophilic addition reactions:

1. Hydrogenation (H₂/Ni)

2. Hydrohalogenation (Markovnikov rule)

3. Anti-Markovnikov addition (HBr + peroxide)

4. Hydration (H₂SO₄)

5. Ozonolysis

6. Polymerisation

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Alkynes

1. Addition of H₂, halogens

2. Hydration → aldehydes/ketones (Keto–enol tautomerism)

3. Oxidation

4. Formation of alkynides (with NaNH₂)

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11. Environmental Chemistry

• Air pollution

• Photochemical smog

• Acid rain

• Greenhouse effect

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⭐ PART B: CLASS 12 ISC CHEMISTRY 2026 – COMPLETE THEORY

1. Solid State

• Types: crystalline, amorphous

• Unit cells (simple, bcc, fcc)

• Packing efficiency

• Defects: Schottky, Frenkel

• Magnetic properties

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2. Solutions

• Raoult’s law

• Ideal/non-ideal solutions

• Colligative properties:

  • RL depression (ΔTf)

  • Boiling elevation (ΔTb)

  • Osmotic pressure Π = CRT

  • Van’t Hoff factor

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3. Electrochemistry

• Conductance (molar, specific)

• Kohlrausch law

• Nernst equation

• Galvanic cell

• Electrolysis, Faraday laws

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4. Chemical Kinetics

• Rate law

• Order & molecularity

• Arrhenius equation

• Half-life formulas

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5. Surface Chemistry

• Adsorption

• Catalysis

• Colloids

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6. General Principles & Processes of Isolation of Elements

• Roasting, calcination

• Concentration methods

• Electrolytic refining

• Thermite process

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7. p-Block Elements

• Group 15, 16, 17, 18

• Oxides, oxyacids

• Halogens

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8. d- and f-Block Elements

• Transition metal properties

• Colour, magnetic behaviour

• Lanthanide contraction

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⭐ 9. Coordination Compounds

• Werner theory

• Coordination number

• Nomenclature

• Isomerism

• VBT & Crystal Field Theory

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⭐ 10. Organic Chemistry (MOST IMPORTANT)

This is the largest portion. Below is super-detailed, reaction-heavy, mechanism-rich content ideal for your standalone page.

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🔥 ALL IMPORTANT ORGANIC REACTION MECHANISMS (ISC + JEE Level)

A. SN1 Reaction Mechanism (Unimolecular Nucleophilic Substitution)

Occurs in: 3° halides
Steps:

1. Formation of carbocation

2. Attack of nucleophile

3. Racemization occurs

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B. SN2 Mechanism (Bimolecular Nucleophilic Substitution)

Occurs in: 1° halides
Steps:

• Backside attack

• Transition state formation

• Inversion of configuration (Walden inversion)

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C. E1 Elimination

• Formation of carbocation

• Loss of proton

• Competes with SN1

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D. E2 Elimination

• One-step process

• Strong base

• Anti-periplanar requirement

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E. Electrophilic Aromatic Substitution (EAS)

Examples:

1. Nitration:
   Benzene + HNO₃/H₂SO₄ → Nitrobenzene

2. Sulphonation:
   Benzene + SO₃ → Benzenesulphonic acid

3. Halogenation:
   FeBr₃ + Br₂ → Bromobenzene

4. Friedel–Crafts Alkylation

5. Friedel–Crafts Acylation

Mechanism:

• Formation of electrophile

• Attack on benzene ring

• Resonance-stabilised arenium ion

• Deprotonation restores aromaticity

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🔥 Important Named Reactions (Complete List)

1. Kolbe’s Electrolysis

2CH₃COO⁻ → C₂H₆ + CO₂

2. Wurtz Reaction

2R–X + Na → R–R

3. Finkelstein Reaction

Halogen exchange (NaI in acetone)

4. Swarts Reaction

R–X → R–F (AgF / SbF₃)

5. Williamson Ether Synthesis

RO⁻ + R'–X → R–O–R'

6. Aldol Condensation

Enolate formation → β-hydroxy aldehyde

7. Cannizzaro Reaction

Aldehydes without α-H → alcohol + acid

8. Sandmeyer Reaction

Ar–N₂⁺ → Ar–Cl/Br/CN

9. Gattermann Reaction

Ar–N₂⁺ → Ar–H (HCl + Cu)

10. Reimer–Tiemann Reaction

Phenol + CHCl₃/KOH → Salicylaldehyde

11. Kolbe Reaction

Phenoxide + CO₂ → Salicylic acid

12. Clemmensen Reduction

R–CO–R → R–CH₂–R (Zn-Hg/HCl)

13. Wolff–Kishner Reduction

R–CO–R → R–CH₂–R (NH₂NH₂/KOH)

14. Rosenmund Reduction

Acid chloride → Aldehyde

15. Etard Reaction

Toluene → Benzaldehyde (CrO₂Cl₂)

16. Friedel–Crafts

Alkylation & acylation (AlCl₃)

17. Perkin Reaction

Aldehyde + anhydride → α,β-unsaturated acid

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⭐ 11. Alcohols, Phenols & Ethers

Reactions:

• Oxidation

• Dehydration

• Substitution

• Esterification

• Kolbe reaction

• Reimer–Tiemann

• Williamson ether synthesis

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⭐ 12. Aldehydes & Ketones

Reactions of carbonyl group:

1. Nucleophilic addition

   • CN⁻ (cyanohydrin)

   • HCN

   • NH₃ derivatives

2. Reduction

   • NaBH₄ / LiAlH₄ → alcohols

3. Oxidation

   • Tollens test

   • Fehling test

4. Cannizzaro reaction

5. Aldol condensation

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⭐ 13. Carboxylic Acids & Derivatives

• Esterification

• Decarboxylation

• HVZ reaction

• Reduction to alcohols

• Formation of acid chloride, anhydride, ester, amide

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⭐ 14. Amines

• Gabriel amine synthesis

• Hoffmann bromamide reaction

• Diazotization

• Coupling reactions

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⭐ 15. Biomolecules

• Carbohydrates

• Proteins (primary to quaternary structure)

• Vitamins

• Enzymes

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⭐ 16. Polymers

• Addition polymers

• Condensation polymers

• Copolymers
  Examples: PVC, PET, Nylon, Bakelite

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⭐ 17. Green Chemistry

• Principles

• Solvent-free synthesis

• Use of catalysts

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⭐ ISC Chemistry Practical 2026 (Complete Overview)

Volumetric Analysis

• Acid-base titration

• Redox titration

• KMnO₄, K₂Cr₂O₇, Na₂S₂O₃

Salt Analysis

• Cations: Pb²⁺, Cu²⁺, Fe²⁺, Fe³⁺, Al³⁺, Ca²⁺

• Anions: CO₃²⁻, SO₃²⁻, SO₄²⁻, Cl⁻, Br⁻, NO₃⁻

Organic Chemistry Experiments

• Identification of functional groups

• Preparation of organic compounds

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⭐ ISC Chemistry 2026 Exam Tips

• Write mechanisms clearly with arrows

• Provide structures, not paragraphs

• For inorganic, mention reactions with oxidation numbers

• For physical chemistry, write formulas + units

• Practice titration calculations thoroughly

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• ISC Chemistry 2026

• ISC Class 12 Chemistry 2026

• ISC Class 11 Chemistry syllabus

• ISC Chemistry reactions

• ISC Chemistry mechanisms

• ISC Chemistry notes 2026

• ISC Chemistry organic reactions

• ISC Chemistry inorganic notes

• ISC Class 12 Chemistry important questions

• ISC Chemistry preparation guide 2026

• ISC 2026 Chemistry practicals

• ISC Chemistry class 11 notes

• ISC Chemistry chapter-wise explanation

• ISC organic chemistry mechanisms

• ISC chemistry full syllabus 2026

• ISC chemistry revision notes

• ISC Chemistry Class 11 and 12 complete notes

• ISC Chemistry all reactions with mechanisms

• ISC Class 12 organic chemistry detailed notes

• ISC Class 11 chemistry theory explanation

• How to score 90+ in ISC Chemistry 2026

• ISC Chemistry 2026 practical file guide

• ISC Chemistry chapter-wise weightage

• ISC Chemistry named reactions explained

• CISCE Chemistry

• ISC Chemistry exam pattern

• Board exam chemistry notes

• Organic chemistry mechanisms for ISC

• ISC chemistry answer writing tips