HSC Chemistry organic chemistry (Module 7): 2026 guide

What Module 7 asks

HSC Chemistry Module 7 (Organic Chemistry) is the most memorisation-heavy module in the course. Around 30% of the exam. Students who treat organic as a system of named functional groups and predictable reactions do well; students who try to derive everything from first principles run out of time.

The content is structured around functional groups and the reactions that interconvert them.

Functional groups

Memorise these. Strong students can draw each from memory in under 5 seconds.

Group	Structure	General formula	Suffix
Alkane	C-C, C-H single bonds	IMATH_5	-ane
Alkene	C=C double bond	IMATH_6	-ene
Alkyne	C≡C triple bond	IMATH_7	-yne
Alcohol	C-OH	IMATH_8	-ol
Aldehyde	-CHO (carbonyl at end)	IMATH_9	-al
Ketone	-C(=O)- (carbonyl middle)	IMATH_10	-one
Carboxylic acid	-COOH	IMATH_11	-oic acid
Ester	-COO-	derived	-oate
Amine	-NH2 (or -NHR, -NR2)	IMATH_12	-amine

Naming organic compounds (IUPAC)

The rules:

1. Identify the longest carbon chain containing the highest-priority functional group. The chain length gives the prefix: meth (1), eth (2), prop (3), but (4), pent (5), hex (6), hept (7), oct (8).
2. Number the carbons from the end nearest the highest-priority functional group.
3. Add the appropriate suffix and locant (number) for the main functional group.
4. Identify substituents (methyl, ethyl, halogen, etc.) and add as prefixes with locants.

Worked example: name CH3-CH(OH)-CH2-CH3.

• Longest chain: 4 carbons (butane).
• Functional group: OH (alcohol, suffix -ol).
• Numbering: closest to OH, so the OH carbon is 2.
• Name: butan-2-ol.

Worked example: name CH3-COOCH2CH3.

• The compound is an ester (CH3-COO-CH2CH3).
• The acyl part (left of -COO-) is from ethanoic acid: name the alkyl part attached to the oxygen first (ethyl), then the acyl part (ethanoate).
• Name: ethyl ethanoate.

Reaction types

Substitution

Alkanes + halogens (Cl2, Br2) in the presence of UV light yield haloalkanes:

Mechanism is free-radical. Reactivity: F > Cl > Br > I.

Addition

Alkenes (and alkynes) undergo addition. The double bond opens and reagent adds across the carbons.

Hydrogenation: alkene + H2 (with Ni catalyst) → alkane.
Halogenation: alkene + Br2 → 1,2-dibromoalkane.
Hydration: alkene + H2O (with H2SO4 catalyst) → alcohol.
Hydrohalogenation: alkene + HX → haloalkane (Markovnikov's rule: H goes to the carbon with more H, X to the carbon with fewer H).

Worked example:

Oxidation

Alcohols are oxidised to aldehydes (primary alcohol with limited oxidiser) or ketones (secondary alcohol). Further oxidation of an aldehyde gives a carboxylic acid.

Common oxidising agents: KMnO4 (potassium permanganate), K2Cr2O7 (potassium dichromate).

(ethanol → ethanal → ethanoic acid)

Tertiary alcohols (no H on the carbon bearing OH) cannot be oxidised by these reagents.

Esterification

A carboxylic acid plus an alcohol, with H2SO4 catalyst, produces an ester plus water:

(ethanoic acid + ethanol → ethyl ethanoate + water)

This is a reversible reaction at equilibrium. Excess of one reagent (or removal of water) shifts the equilibrium toward the ester.

Esters give characteristic fruity smells (banana, pineapple, pear) and are used in fragrances and flavourings.

Polymerisation

Addition polymerisation: alkene monomers join via opening of the C=C double bond. No small molecule is lost.

Common addition polymers: polyethylene (from ethene), polypropylene (from propene), polyvinyl chloride (from chloroethene), polystyrene (from styrene).

Condensation polymerisation: monomers join with loss of a small molecule (usually water). Requires monomers with two reactive functional groups each.

Examples:

• Polyester (e.g. PET): diol + dicarboxylic acid → polyester + water.
• Nylon (e.g. nylon-6,6): diamine + dicarboxylic acid → polyamide + water.

Hydrocarbons as fuels

Combustion of hydrocarbons:

Complete combustion (sufficient oxygen): $C_nH_m + (n + m/4) O_2 \rightarrow n CO_2 + m/2 H_2O$. Produces only CO2 and water.

Incomplete combustion (insufficient oxygen): produces CO (toxic) and/or soot (carbon particles).

Biofuels include bioethanol (from fermentation of sugars), biodiesel (from transesterification of vegetable oils). Strong responses evaluate the trade-offs - reduced fossil fuel use vs land use, ethical and economic concerns.

Common HSC Module 7 traps

Confusing aldehydes and ketones. Aldehyde has the -CHO at the end of the chain. Ketone has -C(=O)- in the middle. Different naming, different reactivity (aldehydes can be oxidised further; ketones cannot).

Forgetting Markovnikov's rule. For asymmetric alkenes plus HX, the H adds to the carbon with MORE H atoms; the X adds to the carbon with FEWER H atoms. This is the major product.

Naming errors with locants. Always number from the end nearest the highest-priority functional group. If both ends give the same locant for the main group, choose the numbering that gives lower locants to substituents.

Mixing up addition and condensation polymerisation. Addition: no small molecule lost. Condensation: water (or similar) released per bond formed.

Forgetting the H2SO4 catalyst in esterification. Many students write the reaction without the catalyst. Markers may not award the mark.

How Module 7 is examined

In the HSC Chemistry exam:

• Multiple choice. Identify a compound from its structure. Name an organic compound. Predict products of a reaction.
• Section II short questions (3-5 marks). Draw a structural formula. Write a balanced equation for a reaction. Identify functional groups.
• Section II extended response (6-9 marks). Multi-step synthesis (e.g. propose a route from ethene to ethyl ethanoate). Spectra interpretation. Polymer evaluation.

Practice strategy

For HSC Chemistry Module 7:

• Term 3. Memorise functional groups and the standard reactions cold. Draw each from memory.
• Term 4. Past papers focused on Module 7. Multi-step synthesis questions repeat patterns; spot them.

Build a flowchart of how the functional groups interconvert (alkene → alcohol → aldehyde → carboxylic acid; carboxylic acid + alcohol → ester). This single diagram answers most of the synthesis questions.

In one sentence

HSC Chemistry Module 7 (Organic Chemistry) rewards systematic memorisation of functional groups, the standard reactions, IUPAC naming rules, and polymer chemistry. Master the functional group interconversion flowchart, drill the named reactions until they are automatic, and practise multi-step synthesis questions until you can navigate them without a reference sheet.