Organic compounds

Practice

Recall it first, then use it — testing yourself builds the memory, where rereading the notes above only feels easier.

Recall and application shuffled together — you have to work out what each item wants before you can answer it, which is the part the exam actually tests. Both kinds feed the same spacing schedule, so anything you miss comes back sooner.

Say the answer out loud before flipping — that attempt is where the learning happens, even when you get it wrong.

Exam-style only. Instant feedback, shuffled each attempt, best score saved on this device.

What actually comes up

Three years of real questions, part by part, with the grade band each part sat at according to that year's marking schedule. Start with the pattern table — it is the fastest way to decide what to revise.

Across 3 years

The pattern — what to prepare

The 2025 paper ↗ Marking schedule ↗

Question 1 — optical isomerism, oxidation & a reaction scheme

Part (a) is about the two enantiomers of glucose, D- and L-glucose, with the structural formula of D-glucose given. Parts (b) and (c) are separate scenarios — see each part.

• a i Label all asymmetric carbon atoms in D-glucose. Achieved
• a ii Explain how D-glucose and L-glucose could be distinguished. Merit
• a iii Explain why D-glucose forms a silver mirror with Tollens' reagent (functional group + reaction type). Merit
• b Convert propanal into N-propylpropanamide, using ONLY the reagents listed (each may be used more than once). Devise the reaction scheme, giving the reagents and the structural formula of the organic product at each step.
  • SOCl₂
  • Cr₂O₇²⁻ / H⁺
  • NaBH₄
  • conc NH₃
  Excellence
• c i A student heated butan-1-ol with EXCESS acidified potassium permanganate (KMnO₄ / H⁺) under reflux for 20 minutes, then distilled the mixture to collect the butanal fraction. No fraction was collected at 73–76 °C. Boiling points: butan-1-ol 118 °C · butanal 74.8 °C · butanoic acid 163 °C. Describe the colour change observed as the reaction is heated, and link it to the type of reaction occurring. Merit
• c ii Explain why no butanal fraction collected at 73–76 °C (over-oxidation under reflux). Excellence
• c iii Why distillation instead of reflux — process + position of the condenser. Excellence

Question 2 — naming, isomerism & compound identification

Part (a) is a name-or-draw table of four compounds. Part (b) identifies three unlabelled colourless liquids — see that part.

• a i Complete the table: name or draw the structural formula. Achieved
• a ii Draw the enantiomers of a chiral compound. Merit
• b Three unlabelled bottles contain ethanol, ethanoyl chloride and ethanal. The student's procedure: Step 1 — add water to all three. Step 2 — add Fehling's solution to the remaining two and heat. Step 3 — add acidified K₂Cr₂O₇ to the remaining one and heat. Complete the observations, reaction type and compound identified for each step, then justify why the steps must be followed in that order. Excellence
• c Draw structural formulae of Compounds A→E from a reaction sequence. Excellence

Question 3 — condensation, hydrolysis & deduction

Two given amino acids are combined into both possible dipeptides and the reaction type named, then Dacron — a polyester used in furniture — has an ester linkage circled and its behaviour under reflux with NaOH explained. Part (b) is pure deduction: three lettered compounds sorted by their reactions, then two structures built from a molecular formula and a list of properties.

• a i Draw the two dipeptides that can form from two given amino acids. Merit
• a ii Identify and explain the reaction forming the dipeptides (condensation). Merit
• a iii Circle an ester linkage in the Dacron polymer. Achieved
• a iv Identify and explain the reaction when Dacron is heated under reflux with NaOH — draw the products. Excellence
• b i From W, X, Y identify which has cis-trans + reacts with SOCl₂ + reduces with NaBH₄ — and why the others fail. Excellence
• b ii Draw Compound S (C₅H₁₀O₃: can oxidise to a ketone, forms a cyclic ester). Merit
• b iii Draw Compound T (C₅H₉Br: branched, chiral, secondary haloalkane, reacts with Br₂ water). Excellence

The 2024 paper ↗ Marking schedule ↗

Question 1 — optical isomerism & condensation polymers

Part (a) is about 2-chlorobutane, whose structural formula is given. Parts (b) and (c) are separate scenarios — see each part.

• a i Draw the enantiomers of 2-chlorobutane. Merit
• a ii Explain why 2-chlorobutane can exist as enantiomers. Merit
• a iii Convert 2-chlorobutane into butanamide. For each step give the reagents AND the structural formula of the organic product. Devise the reaction scheme, giving the reagents and the structural formula of the organic product at each step. Excellence
• b i Polylactic acid (PLA) is a polyester used in medical implants, tissue engineering and 3D printing. It is made from lactic acid, CH₃CH(OH)COOH. Draw a section of the PLA chain showing THREE repeating units. Merit
• b ii Identify and explain the reaction that forms PLA (condensation polymerisation). Merit
• c i Circle the amide (peptide) linkage in the dipeptide. Achieved
• c ii Identify and justify the type of reaction (acidic hydrolysis) to the two products. Excellence
• c iii Draw the organic products of basic (NaOH) hydrolysis of the dipeptide. Merit

Question 2 — naming, isomers & identification

A four-row table of structural formulae and IUPAC names (methyl propanoate, an acyl chloride, 2-hydroxybutanoyl chloride), three constitutional isomers containing C=O, a reaction flowchart to complete, and three unlabelled colourless liquids to identify from a sequence of tests.

• a i Complete the name/draw table (methyl propanoate, an acyl chloride, 2-hydroxybutanoyl chloride). Achieved
• a ii Draw three constitutional isomers of Compound C that contain a C=O. Merit
• b Complete the reaction flowchart. Merit
• c i Identify the three compounds from observations (dichromate, Tollens, Fehling, KMnO₄, Br₂ water). Excellence
• c ii Justify each identification; relate observations to functional groups and reaction types. Excellence

Question 3 — esters & deduction

A six-step laboratory preparation of pure ethyl propanoate — concentrated H₂SO₄, reflux, sodium carbonate, separation, drying, distillation — with a question on the purpose of each stage, then compound deduction from properties.

• propanoic acid + ethanol + conc. H₂SO₄
• heated under reflux 30 min
• Na₂CO₃ added until bubbling stops
• distilled to purify

• a i Describe the function of concentrated H₂SO₄ in esterification. Achieved
• a ii Give two reasons the mixture was heated under reflux. Merit
• a iii Why was sodium carbonate added? Merit
• a iv Explain how distillation purified the ethyl propanoate, using the boiling points. Excellence
• b i Choose the compound with all of: no enantiomers, silver mirror, turns litmus blue — explain. Excellence
• b ii Draw the isomer of C₅H₉OCl that is branched, chiral, gives steamy fumes with water. Merit
• b iii Draw the isomer of C₄H₇OBr with cis-trans, straight chain, oxidises to a non-reducing product. Excellence

The 2023 paper ↗ Marking schedule ↗

Question 1 — optical isomerism & reaction schemes

Part (a) is about 2-hydroxybutanoic acid, CH₃CH₂CH(OH)COOH, whose structural formula is given. Parts (b) and (c) are separate scenarios — see each part.

• a i Circle the asymmetric carbon atom in 2-hydroxybutanoic acid; describe the structural feature of enantiomers. Achieved
• a ii Draw the two 3D enantiomers of 2-hydroxybutanoic acid. Merit
• b Convert pentan-2-one into pentyl ethanoate. For each step give the reagents AND conditions, and the structural formula of the organic product. Devise the reaction scheme, giving the reagents and the structural formula of the organic product at each step. Excellence
• c i Six numbered structural formulae are given (see the paper). Two sets of observations are listed: (1) bubbles on adding Na₂CO₃ solution, and purple KMnO₄ turning to a brown solid — soluble in water. (2) turns damp red litmus paper blue, and blue solution to an orange-red solid when heated with Fehling's reagent — soluble in water. Match each set of observations to a compound number from the table. Achieved
• c ii Relate observations to functional groups + reaction types to identify a carboxylic acid (with C=C) and an amine (with –CHO). Excellence

Question 2 — oxidation, distinguishing & condensation

A student has two test tubes, one containing propan-1-ol and the other propan-2-ol, adds acidified potassium permanganate to each, and warms them in a water bath.

• a i Describe the colour change occurring in both test tubes. Achieved
• a ii Distinguish propanal from propanone using Tollens' reagent (draw the product). Merit
• b Draw functional groups / structural isomers. Merit
• c i Draw the two dipeptides from the two amino acids (condensation). Excellence
• c ii Explain the condensation reaction and why a water molecule is released. Merit
• c iii Draw the hydrolysis products of the dipeptide. Merit

Question 3 — reflux & hydrolysis

A naming and structure table (pentan-3-one, an acyl chloride, 2-methylbutanamide), then the basic hydrolysis of a triglyceride found in fats and oils — including choosing the right apparatus for it — and finally a branched C₄H₉O₃N compound to deduce through a chain of reactions.

• triglyceride of octadecanoic acid
• Compound C: C₄H₉O₃N, branched, exists as enantiomers

• a Complete the table to show either the structural formula or the IUPAC name for each organic molecule: pentan-3-one, a given acyl chloride, and 2-methylbutanamide. Achieved
• b i Draw both organic products of a strong-base hydrolysis. Excellence
• b ii Select B (reflux over distillation) — give two valid reasons. Merit
• c Compound C is an enantiomer that undergoes acidic hydrolysis — draw the conversion scheme. Excellence

Read the last column as a to-do list. Optical isomerism and condensation/hydrolysis are in every paper; Question 1 often opens with drawing enantiomers, and a later question with a "which compound has all these properties" deduction.

Past exams & resources

⏱ Timed opens the paper and starts a countdown matching the exam length. Official NZQA PDFs. If a link 404s, that year’s paper may sit under a slightly different code: browse the NZQA subject page.