Because of tetravalency (forms four covalent bonds) and catenation (ability to form long chains/rings with itself). This produces a huge variety of compounds with different sizes and functional groups.
Covalent Bonding
Functional Groups
Soaps & Detergents
Nomenclature
NCERT Class 10 — Chapter 4: Carbon and its Compounds
A covalent bond forms by sharing electron pairs between atoms (usually non-metals). In contrast, ionic bonds form by complete transfer of electrons from a metal to a non-metal, producing ions.
Methane has four C–H single covalent bonds arranged tetrahedrally around carbon.
- Diamond: 3D network; each C bonded to 4 C; very hard; electrical insulator; used in cutting tools.
- Graphite: layered structure; each C bonded to 3 C (sp²); soft, slippery; good conductor due to delocalised electrons; used in electrodes and lubricants.
Catenation is the ability of an element to form bonds with itself, resulting in chains or rings. Carbon forms long chains (e.g., alkanes) and rings (e.g., cyclohexane), enabling complex organic molecules.
A homologous series is a family of compounds with the same functional group and general formula, with successive members differing by –CH₂–. They show gradual change in physical properties and similar chemical properties.
Saturated: alkanes (single bonds), e.g., methane, ethane. Unsaturated: alkenes (C=C) like ethene; alkynes (C≡C) like ethyne.
- Alcohol: –OH
- Aldehyde: –CHO
- Ketone: >C=O
- Carboxylic acid: –COOH
- Halides: –X (F, Cl, Br, I)
- Amino: –NH₂
- Select the longest carbon chain (parent).
- Number to give lowest locants to multiple bonds/functional groups.
- Name substituents with positions; assemble as
prefix + parent + suffix.
Examples: CH₃–CH₂–OH → ethanol; (CH₃)₂CH–CH₃ → 2-methylpropane.
Complete (excess O₂): CO₂ + H₂O, blue flame, more energy. Incomplete (limited O₂): CO and soot (C), yellow smoky flame. Example: CH₄ + 2O₂ → CO₂ + 2H₂O.
Oxidising agents like alkaline KMnO₄/K₂Cr₂O₇ convert alcohols to acids: CH₃CH₂OH → CH₃COOH (ethanol to acetic acid), with gain of oxygen.
Unsaturated oils react with H₂ in presence of Ni catalyst to form saturated fats (e.g., making vanaspati ghee). This raises melting point and hardness.
In substitution, an atom/group in a molecule is replaced by another. Example: CH₄ + Cl₂ → CH₃Cl + HCl (in presence of sunlight/UV).
Use bromine water (orange to colourless) or acidified KMnO₄ (purple to colourless). Alkenes/alkynes decolourise; alkanes do not.
- Colourless, volatile liquid; b.p. ≈ 78 °C; miscible with water.
- Used as solvent, fuel, in sanitizers and medicines; denatured for industrial use.
Pungent smelling liquid; forms vinegar (~5–8% solution); freezes near 16.6 °C (glacial acetic acid). Reacts with bases to form acetates and water.
Alcohol + Acid ⇌ Ester + Water (conc. H₂SO₄ catalyst). Example: CH₃CH₂OH + CH₃COOH ⇌ CH₃COOCH₂CH₃ + H₂O (sweet smell).
Hydrolysis of an ester with a base (NaOH/KOH) to form soap (sodium/potassium salt of fatty acid) and glycerol.
Soap molecules have a hydrophobic tail (attracted to grease) and a hydrophilic head (attracted to water). They form micelles that lift dirt into water.
- Soaps: sodium/potassium salts of fatty acids; form scum in hard water (Ca²⁺/Mg²⁺).
- Detergents: sodium salts of sulphonic acids; work in hard water; produce more foam; some types less biodegradable.
Compounds with the same molecular formula but different structures. C₄H₁₀: n-butane and isobutane (2-methylpropane).
They consist of neutral molecules with weak intermolecular forces and no free ions/electrons for conduction (exceptions: graphite, conjugated systems).
Ethene has a C=C double bond; planar structure around each carbon.
Linear molecule with a C≡C triple bond.
- Propane
- Propanoic acid
- Dimethyl ether
- Chloroethane
Effervescence due to H₂ gas; sodium ethoxide is formed: 2C₂H₅OH + 2Na → 2C₂H₅ONa + H₂↑.
Vigorous effervescence due to CO₂: CH₃COOH + NaHCO₃ → CH₃COONa + H₂O + CO₂↑ (turns limewater milky).
Alkanes: CₙH₂ₙ₊₂; Alkenes: CₙH₂ₙ; Alkynes: CₙH₂ₙ₋₂.
C₂H₅OH + 3O₂ → 2CO₂ + 3H₂O.
Due to incomplete combustion and a higher C:H ratio producing unburnt carbon particles (soot), especially in unsaturated/aromatic compounds.
- Aldehyde (–CHO)
- Ketone (>C=O)
- Alcohol (–OH)
- Carboxylic acid (–COOH)
By heating ethanol with conc. H₂SO₄ or over Al₂O₃ (catalyst) to eliminate water: C₂H₅OH → C₂H₄ + H₂O.
It gets oxidised to ethane-1,2-diol (ethylene glycol); solution decolourises (Baeyer test).
Joining many small monomers to form a large polymer. Examples: ethene → polyethene; vinyl chloride → PVC; tetrafluoroethene → PTFE (Teflon).
Their sulphate/sulphonate heads do not precipitate with Ca²⁺/Mg²⁺ ions; hence no scum formation and better cleaning.
- Tetravalency and catenation.
- Strong C–C and C–H bonds; small atomic size.
- Ability to form single/double/triple bonds and various functional groups.
- C₃H₈
- C₄H₈
- C₂H₂
- C₅H₁₂O
- Ethanol: CH₃–CH₂–OH
- Propanol: CH₃–CH₂–CH₂–OH (or CH₃–CH(OH)–CH₃)
- Propanoic acid: CH₃–CH₂–COOH
- Acetone (propanone): CH₃–CO–CH₃
- Ethanal: CH₃–CHO
Alkanes are saturated (no multiple bonds), so substitution replaces H atoms. Alkenes have a π-bond that can break and add atoms across C=C (addition).
They are non-polar molecules; water is polar. By “like dissolves like”, non-polar compounds dissolve in non-polar organic solvents.
- Ethanol + oxidising agent → acetic acid + water.
- Alcohol + carboxylic acid ⇌ ester + water (acid catalyst).
- Ester + base → soap + alcohol (saponification).
- Ethene + hydrogen → ethane (Ni catalyst).
1,2-Dibromoethane (addition across C=C). Bromine solution decolourises.
- Aldehyde: –CHO at chain end; suffix -al (ethanal).
- Ketone: >C=O within chain; suffix -one (propanone).
- Propan-1-ol
- Propan-2-ol
Strong hydrogen bonding leads to an ordered dimeric structure and higher freezing point than many organics.
- Ethanol: fuel/blending with petrol; hand sanitizers/solvent.
- Acetic acid: vinegar (food preservative); manufacture of esters/plastics.
CH₄ (alkane) and C₄H₁₀ are saturated; C₃H₆ (alkene) and C₂H₂ (alkyne) are unsaturated.
(a) Alkene + water (elimination). (b) Alkane (addition of H₂).
Soaps react with Ca²⁺/Mg²⁺ to form insoluble salts (scum). Detergents do not form such precipitates.
They have high calorific values and burn readily (with sufficient oxygen) to release energy. Examples: methane (CNG), ethanol–petrol blends.