CLASS 12 • ORGANIC CHEMISTRY
Exam-focused revision notes • Arranged as exactly 5 topic cards per content page
How to use: Read the rule, memorize the examples, then practise naming/reaction questions. The notes
below follow the topics visible in the provided revision image and the uploaded lecture content; unclear
transcript details are not silently expanded.
1. IUPAC Nomenclature
Core order: Substituent(s) → Root word (number of carbon atoms) → Bond type suffix → Principal functional-group
suffix.
Root words: 1 meth-, 2 eth-, 3 prop-, 4 but-, 5 pent-, 6 hex-, 7 hept-, 8 oct-, 9 non-, 10 dec-.
Bond suffixes: Single bond: -ane; double bond: -ene; triple bond: -yne. Choose the longest suitable parent chain and
number it to give the lowest possible locants to the principal group/multiple bond.
Functional groups shown in the notes: Halogen: chloro-/bromo-/iodo-; alcohol: -ol; aldehyde: -al; ketone: -one;
carboxylic acid: -oic acid.
Examples: CH₃CH₂OH = ethanol; CH₃COCH₃ = propanone; CH₃CH(Cl)CH₃ = 2-chloropropane; CH₃CH₂COOH =
propanoic acid.
EXAM TIP: Exam tip: Identify the principal functional group first, then parent chain, numbering,
substituents and suffix.
2. Hydrocarbons and Carbon-Chain Prefixes
Hydrocarbons: Contain only carbon and hydrogen.
Alkanes: Single C–C bonds; general formula CₙH₂ₙ₊₂; suffix -ane.
Alkenes: At least one C=C double bond; open-chain formula CₙH₂ₙ for one double bond; suffix -ene.
Alkynes: At least one C≡C triple bond; open-chain formula CₙH₂ₙ₋₂ for one triple bond; suffix -yne.
Prefixes: Meth-, eth-, prop-, but-, pent-, hex-, hept-, oct-, non-, dec- correspond to 1–10 carbon atoms.
EXAM TIP: Memory trick: Alkane +2; alkene no extra 2; alkyne −2 (relative to CₙH₂ₙ).
3. Functional Groups and Naming
Functional group: The group that influences characteristic properties and naming of an organic compound.
Halogen: –Cl, –Br, –I are named as prefixes: chloro-, bromo-, iodo-. Example: chloroethane.
Alcohol: –OH; suffix -ol. Example: ethanol; butan-2-ol has OH on carbon 2.
Aldehyde and ketone: –CHO at the end: -al (propanal); >C=O within the chain: -one (propanone).
Carboxylic acid: –COOH; suffix -oic acid. Example: ethanoic acid. The carboxyl carbon is included in the chain count.
EXAM TIP: Common correction: not every C=O compound is a ketone—aldehydes and carboxylic acids
also contain carbonyl-related structures.
4. Haloalkanes and Haloarenes
Definitions: Haloalkane: R–X, where a halogen replaces hydrogen in an alkane. Haloarene: Ar–X, where halogen is
directly attached to an aromatic ring.
Classification by number of halogens: Monohalo: one X; dihalo: two X; polyhalo: three or more X.
Classification by carbon bearing X: Primary, secondary and tertiary haloalkanes depend on whether the carbon
attached to X is bonded to 1, 2 or 3 other carbons.
Position-based terms: Vinylic: X on an sp² carbon of C=C; allylic: next to C=C; aryl: directly on aromatic ring;
benzylic: on the carbon next to an aromatic ring.
Key distinction: Chlorobenzene is a haloarene; benzyl chloride is a benzylic halide, not a haloarene.
EXAM TIP: Keep the atom directly bonded to the halogen in mind when classifying.
Class 12 Organic Chemistry • 5 topics per page • Page 1
, 5. Preparation of Haloalkanes
From alcohols using HX: ROH + HX → RX + H₂O; the notes mention HCl with anhydrous ZnCl₂ (Lucas reagent) in the
relevant case.
Using phosphorus halides: Alcohols can react with PCl₃/PCl₅ to form chloroalkanes; the source also lists SOCl₂,
producing SO₂ and HCl as gases.
Direct halogenation: RH + Cl₂ —sunlight→ RCl + HCl; free-radical substitution can give mixtures of products.
Addition to alkenes: HX adds across C=C. The notes distinguish Markovnikov addition from the peroxide effect for
HBr.
Named reactions: Finkelstein: alkyl chloride/bromide + NaI in acetone → alkyl iodide. Swarts: used for preparing alkyl
fluorides.
EXAM TIP: Check the conditions and reagent carefully; direct halogenation may not be selective.
Class 12 Organic Chemistry • 5 topics per page • Page 2
Exam-focused revision notes • Arranged as exactly 5 topic cards per content page
How to use: Read the rule, memorize the examples, then practise naming/reaction questions. The notes
below follow the topics visible in the provided revision image and the uploaded lecture content; unclear
transcript details are not silently expanded.
1. IUPAC Nomenclature
Core order: Substituent(s) → Root word (number of carbon atoms) → Bond type suffix → Principal functional-group
suffix.
Root words: 1 meth-, 2 eth-, 3 prop-, 4 but-, 5 pent-, 6 hex-, 7 hept-, 8 oct-, 9 non-, 10 dec-.
Bond suffixes: Single bond: -ane; double bond: -ene; triple bond: -yne. Choose the longest suitable parent chain and
number it to give the lowest possible locants to the principal group/multiple bond.
Functional groups shown in the notes: Halogen: chloro-/bromo-/iodo-; alcohol: -ol; aldehyde: -al; ketone: -one;
carboxylic acid: -oic acid.
Examples: CH₃CH₂OH = ethanol; CH₃COCH₃ = propanone; CH₃CH(Cl)CH₃ = 2-chloropropane; CH₃CH₂COOH =
propanoic acid.
EXAM TIP: Exam tip: Identify the principal functional group first, then parent chain, numbering,
substituents and suffix.
2. Hydrocarbons and Carbon-Chain Prefixes
Hydrocarbons: Contain only carbon and hydrogen.
Alkanes: Single C–C bonds; general formula CₙH₂ₙ₊₂; suffix -ane.
Alkenes: At least one C=C double bond; open-chain formula CₙH₂ₙ for one double bond; suffix -ene.
Alkynes: At least one C≡C triple bond; open-chain formula CₙH₂ₙ₋₂ for one triple bond; suffix -yne.
Prefixes: Meth-, eth-, prop-, but-, pent-, hex-, hept-, oct-, non-, dec- correspond to 1–10 carbon atoms.
EXAM TIP: Memory trick: Alkane +2; alkene no extra 2; alkyne −2 (relative to CₙH₂ₙ).
3. Functional Groups and Naming
Functional group: The group that influences characteristic properties and naming of an organic compound.
Halogen: –Cl, –Br, –I are named as prefixes: chloro-, bromo-, iodo-. Example: chloroethane.
Alcohol: –OH; suffix -ol. Example: ethanol; butan-2-ol has OH on carbon 2.
Aldehyde and ketone: –CHO at the end: -al (propanal); >C=O within the chain: -one (propanone).
Carboxylic acid: –COOH; suffix -oic acid. Example: ethanoic acid. The carboxyl carbon is included in the chain count.
EXAM TIP: Common correction: not every C=O compound is a ketone—aldehydes and carboxylic acids
also contain carbonyl-related structures.
4. Haloalkanes and Haloarenes
Definitions: Haloalkane: R–X, where a halogen replaces hydrogen in an alkane. Haloarene: Ar–X, where halogen is
directly attached to an aromatic ring.
Classification by number of halogens: Monohalo: one X; dihalo: two X; polyhalo: three or more X.
Classification by carbon bearing X: Primary, secondary and tertiary haloalkanes depend on whether the carbon
attached to X is bonded to 1, 2 or 3 other carbons.
Position-based terms: Vinylic: X on an sp² carbon of C=C; allylic: next to C=C; aryl: directly on aromatic ring;
benzylic: on the carbon next to an aromatic ring.
Key distinction: Chlorobenzene is a haloarene; benzyl chloride is a benzylic halide, not a haloarene.
EXAM TIP: Keep the atom directly bonded to the halogen in mind when classifying.
Class 12 Organic Chemistry • 5 topics per page • Page 1
, 5. Preparation of Haloalkanes
From alcohols using HX: ROH + HX → RX + H₂O; the notes mention HCl with anhydrous ZnCl₂ (Lucas reagent) in the
relevant case.
Using phosphorus halides: Alcohols can react with PCl₃/PCl₅ to form chloroalkanes; the source also lists SOCl₂,
producing SO₂ and HCl as gases.
Direct halogenation: RH + Cl₂ —sunlight→ RCl + HCl; free-radical substitution can give mixtures of products.
Addition to alkenes: HX adds across C=C. The notes distinguish Markovnikov addition from the peroxide effect for
HBr.
Named reactions: Finkelstein: alkyl chloride/bromide + NaI in acetone → alkyl iodide. Swarts: used for preparing alkyl
fluorides.
EXAM TIP: Check the conditions and reagent carefully; direct halogenation may not be selective.
Class 12 Organic Chemistry • 5 topics per page • Page 2
