ICSE Class 10 Chemistry: Organic Chemistry Introduction 2026

Why Carbon is Special

• Tetravalency: carbon forms 4 covalent bonds; unique bonding versatility
• Catenation: ability to bond with other carbon atoms — chains, branches, rings
• Over 10 million organic compounds known vs. ~100,000 inorganic compounds

Homologous Series

• Series of compounds with same functional group, general formula, differing by –CH₂– unit
• Properties change gradually along series; chemical reactions are similar
• Examples: alkanes (CₙH₂ₙ₊₂), alkenes (CₙH₂ₙ), alkynes (CₙH₂ₙ₋₂)

Functional Groups

• Hydroxyl –OH (alcohols), carboxyl –COOH (acids), aldehyde –CHO, ketone >C=O
• Amino –NH₂ (amines), halide –X (haloalkanes), ester –COO–
• Functional group determines reactivity and properties of the organic compound

IUPAC Nomenclature Basics

• Identify longest carbon chain (parent chain) → name the alkane base
• Number chain from end closest to functional group or substituent
• Name substituents (methyl, ethyl, bromo) with locant prefix: 2-methylpropane

Alkanes — Properties and Reactions

• Saturated hydrocarbons; burn in O₂: CH₄ + 2O₂ → CO₂ + 2H₂O
• Substitution reaction with halogens in UV light: CH₄ + Cl₂ → CH₃Cl + HCl
• Physical properties: increasing bp with chain length; non-polar; immiscible with water

Alkenes and Alkynes

• Alkenes contain C=C double bond; undergo addition reactions
• Br₂ water test: orange decolourises with alkene (addition of Br₂ across double bond)
• Alkynes: C≡C triple bond; more unsaturated; higher reactivity than alkenes

Exam Tips — Organic Chemistry

• Learn general formulas and draw structural formulas of first four members of each series
• Addition vs substitution reactions: alkenes — addition; alkanes — substitution
• ICSE focuses on ethanol, ethanoic acid, and ethene reactions