Chemistry • Year 12 • Module 7 • Lesson 20
Organic Reactions Mastery
Recall every Module 7 reaction type, its reagents, conditions and products. Lock in the vocabulary and conditions that cost marks at Band 3–4 when left incomplete.
1. Complete the master conditions table
Fill in every blank cell. This is the core reference table for Module 7 — if you can reproduce it from memory you are exam-ready. 20 marks (1 per cell)
| Reaction | Starting material | Reagent | Catalyst | Key conditions / temp | Arrow type | Product |
|---|---|---|---|---|---|---|
| Hydrogenation of alkene | Alkene | Ni, Pd or Pt | → | Alkane | ||
| Halogenation (addition) | Alkene | Br2 or Cl2 | Room temp; fume cupboard | → | ||
| Hydrohalogenation | Alkene | None | Room temp (Markovnikov applies) | → | Haloalkane | |
| ⚠ Hydration of alkene | Alkene | H2O (steam) | H3PO4 or dil. H2SO4 | Alcohol | ||
| ⚠ Alkane halogenation | Alkane | Cl2 or Br2 | UV light (energy source, not catalyst) | → | Haloalkane + HX (mixture) | |
| Haloalkane → alcohol | Haloalkane | None | Reflux | → | Alcohol + NaX | |
| Dehydration of alcohol | Alcohol | conc. H2SO4 or H3PO4 | Acid catalyst | 170–230°C, atmospheric P | → | |
| ⚠ 1° alcohol → aldehyde | Primary alcohol | K2Cr2O7/H2SO4 | H2SO4 (acidified) | → | Aldehyde (orange → green) | |
| ⚠ 1° alcohol → carboxylic acid | Primary alcohol | K2Cr2O7/H2SO4 (excess) | H2SO4 | → | Carboxylic acid (orange → green) | |
| 2° alcohol → ketone | Secondary alcohol | K2Cr2O7/H2SO4 | H2SO4 | Reflux | → | |
| 3° alcohol with oxidant | Tertiary alcohol | K2Cr2O7/H2SO4 | — | Any | — | |
| ⚠ Esterification | Carboxylic acid + alcohol | Carboxylic acid + alcohol | Heat, reflux | Ester + H2O (yield <100%) | ||
| Ester hydrolysis (acid) | Ester + H2O | H2O + dil. H2SO4 | H2SO4 | Reflux | Carboxylic acid + alcohol | |
| Saponification | Ester (fat/oil) | None (NaOH = reagent) | Reflux | → | Carboxylate salt + alcohol | |
| Fermentation | Glucose solution | Glucose (C6H12O6) | Yeast (zymase enzyme) | → | Ethanol + CO2 | |
| ⚠ Alkyne hydration | Alkyne | H2O | ~60°C | → | Ketone (ethanal from HC≡CH) |
⚠ = highest-frequency penalty rows in HSC marking reports. If you leave any cell blank in these rows, assume 0 marks on that component.
Stuck? Revisit Lesson 20 Card 1 (Complete Reference Table). Cover the table and re-attempt from memory.2. Term–definition match
Match each definition in the left column to the correct term from the box below. Write the term in the right column. 10 marks
Term box: substitution • addition • elimination • condensation • saponification • hydrolysis • esterification • oxidation • fermentation • halogenation
| # | Definition | Term |
|---|---|---|
| 2.1 | A reaction in which one atom or group replaces another; alkane + halogen (free-radical) or haloalkane + OH− (nucleophilic). | |
| 2.2 | A reaction in which two reactants combine across a multiple bond to form a single product — e.g. alkene + H2, HX, X2, or H2O. | |
| 2.3 | Loss of atoms or groups from adjacent carbons to form a multiple bond; e.g. alcohol → alkene by dehydration. | |
| 2.4 | Two molecules combine with loss of a small molecule (often H2O); includes esterification and amide formation. | |
| 2.5 | The reaction of a carboxylic acid with an alcohol, with conc. H2SO4 catalyst, to form an ester and water (reversible). | |
| 2.6 | The reaction of an ester (fat/oil) with conc. NaOH(aq) or KOH(aq) under reflux, producing a carboxylate salt and alcohol; used in soap manufacture. | |
| 2.7 | The breaking of a chemical bond by reaction with water — e.g. ester + H2O → carboxylic acid + alcohol under acidic conditions. | |
| 2.8 | In organic chemistry: primary alcohol → aldehyde → carboxylic acid; secondary alcohol → ketone; using K2Cr2O7/H2SO4. | |
| 2.9 | The anaerobic breakdown of glucose by yeast (zymase) at ~35°C, producing ethanol and carbon dioxide. | |
| 2.10 | An addition reaction involving halogens (Cl2 or Br2) adding across a double or triple bond at room temperature without a catalyst. |
3. True or false — with correction
Circle T or F. If false, write the corrected version on the line provided. 12 marks (1 T/F, 1 correction)
3.1 UV light acts as a catalyst in the free-radical halogenation of alkanes. T / F
3.2 The esterification of propanoic acid with ethanol produces a single-arrow irreversible product because K2Cr2O7 is added as a catalyst. T / F
3.3 Reflux keeps the reaction mixture at the boiling point while preventing loss of volatile components, allowing reactions to proceed to higher yield. T / F
3.4 A tertiary alcohol gives an orange-to-green colour change with acidified K2Cr2O7, producing a ketone as product. T / F
3.5 Hydration of alkenes requires high pressure (~65 atm) because the equilibrium favours the alcohol side only at elevated pressure. T / F
3.6 Using aqueous NaOH with a haloalkane produces a substitution product (alcohol), whereas using alcoholic NaOH produces an elimination product (alkene). T / F
4. Fill-in-the-blank paragraph
Complete the paragraph using the word bank below. Each term is used once only. 8 marks
Word bank: distillation • reflux • aldehyde • carboxylic acid • orange • green • excess • equilibrium
When a primary alcohol is oxidised with K2Cr2O7/H2SO4, the colour of the solution changes from ____________ to ____________, indicating that oxidation has occurred. To obtain only the ____________ (the partially oxidised product), a limited amount of oxidant must be used and the equipment must be set up for ____________, so that the volatile product is removed from the flask as it forms. If the goal is the fully oxidised product (a ____________), ____________ oxidant is used and the flask is fitted for ____________ instead, keeping all reagents in contact. Esterification differs from both of these because it reaches a chemical ____________ — the reaction does not go to completion and the yield is always less than 100%.
Q1 — Master conditions table
Hydrogenation: Reagent = H2 (gas); Conditions = ~150–200°C, high pressure.
Halogenation (addition): Catalyst = none; Product = dihaloalkane.
Hydrohalogenation: Reagent = HCl, HBr, or HI.
Hydration of alkene: Conditions = ~300°C, HIGH PRESSURE (~65 atm); Arrow = ⇌ (reversible).
Alkane halogenation: Catalyst = none (UV light is energy source, NOT catalyst).
Haloalkane → alcohol: Reagent = NaOH(aq) — must specify AQUEOUS.
Dehydration: Product = alkene + H2O.
1° alcohol → aldehyde: Conditions = DISTILLATION (removes aldehyde before over-oxidation).
1° alcohol → carboxylic acid: Conditions = REFLUX with excess oxidant.
2° alcohol → ketone: Product = ketone + H2O (orange → green).
3° alcohol: Product = NO REACTION (solution stays orange).
Esterification: Catalyst = conc. H2SO4; Arrow = ⇌ (reversible).
Ester hydrolysis (acid): Arrow = ⇌ (reversible).
Saponification: Reagent = conc. NaOH(aq) or KOH(aq).
Fermentation: Conditions = ~35°C, ANAEROBIC (sealed vessel).
Alkyne hydration: Catalyst = dil. H2SO4 AND Hg2+ (BOTH required).
Q2 — Term–definition matches
2.1 substitution • 2.2 addition • 2.3 elimination • 2.4 condensation • 2.5 esterification • 2.6 saponification • 2.7 hydrolysis • 2.8 oxidation • 2.9 fermentation • 2.10 halogenation
Q3 — True / false with corrections
3.1 False. Correction: UV light is an energy source (initiator for free-radical chain reaction), not a catalyst. Writing “UV light (catalyst)” is one of the four most-penalised errors in HSC Module 7 marking.
3.2 False. Correction: Esterification uses conc. H2SO4 as catalyst (not K2Cr2O7). The reaction IS reversible and must use the ⇌ arrow — yield is less than 100% at equilibrium.
3.3 True.
3.4 False. Correction: A tertiary alcohol does NOT react with K2Cr2O7/H2SO4 — the solution stays orange. There is NO colour change and NO organic product. Ketones are the product of oxidising secondary (not tertiary) alcohols.
3.5 True. (High pressure shifts the equilibrium toward the alcohol product and increases the rate of the gas-phase reaction.)
3.6 True.
Q4 — Cloze paragraph
In order: orange → green → aldehyde → distillation → carboxylic acid → excess → reflux → equilibrium