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S6 Chemistry: Organic Synthesis Routes (Paper 1: Basics)
S6 Chemistry: Organic Synthesis Routes (Paper 1: Basics)
Ten items on reagents for dehydration, hydration, oxidation and substitution, with a theoretical yield, answers and notes.
Direct answers Answers in order: dehydration with concentrated sulphuric acid at 170 C, distillation, ethanol, steam with phosphoric acid, a silver mirror, no silver mirror, 3.0 g, 5.5 g, unchanged, ethene by elimination.
01 Paper details (check answers afterwards)
| Item | Detail |
|---|---|
| Questions | 10 |
| Suggested time | 20 |
| Difficulty mix | Foundation 3 · Intermediate 3 · Challenge 3 · Error redo 1 |
| Chapter | Chapter: S6 Chemistry: Organic Synthesis Routes |
| Level | S6 |
02 Questions (10 items)
- FoundationWhich reaction and condition convert ethanol into ethene?
- FoundationOxidising ethanol to ethanal with acidified dichromate: should the apparatus use distillation or reflux?
- FoundationBromoethane is refluxed with aqueous sodium hydroxide. What is the main product?
- IntermediateWhat reagents and conditions convert ethene into ethanol?
- IntermediateEthanal is warmed with Tollens reagent. What is observed?
- IntermediatePropanone is warmed with Tollens reagent. What is the result?
- Challenge2.3 g of ethanol is fully oxidised to ethanoic acid. What is the theoretical mass? (Ethanol 46, acid 60)
- Challenge10.9 g of bromoethane reacts fully with potassium cyanide. What mass of propanenitrile is expected? (109 and 55)
- ChallengePropanenitrile is hydrolysed to propanoic acid. How does the number of carbon atoms change?
- Error redoError replay: a student says bromoethane with ethanolic sodium hydroxide gives ethanol. What is correct?
03 Answers and one-line notes
| # | Answer | One-line note |
|---|---|---|
| 1 | Dehydration with concentrated sulphuric acid heated to 170 C | Concentrated sulphuric acid removes the hydroxyl group and a hydrogen from the next carbon to give a C=C bond. |
| 2 | Distillation, so the ethanal distils out at once | Ethanal boils low and leaves before it can be oxidised again, whereas reflux carries the oxidation on to ethanoic acid. |
| 3 | Ethanol | The aqueous route is nucleophilic substitution by hydroxide, and only the ethanolic route eliminates to ethene. |
| 4 | Steam with phosphoric acid catalyst under heat and pressure | This is the hydration addition of an alkene: water adds across the double bond and the product is ethanol. |
| 5 | A silver mirror forms on the tube wall | An aldehyde reduces silver ions to metallic silver, and a ketone gives no such reaction. |
| 6 | No silver mirror, the reagent is unchanged | The carbonyl carbon of a ketone carries no hydrogen atom, so Tollens reagent cannot oxidise it. |
| 7 | 3.0 g | Moles are 2.3 over 46, giving 0.050, and that multiplied by 60 is 3.0 g. |
| 8 | 5.5 g | 0.10 mol of bromoethane gives 0.10 mol of nitrile, and 0.10 multiplied by 55 is 5.5 g. |
| 9 | It stays the same, still three | Hydrolysis turns the nitrile group into a carboxyl group and the nitrile carbon stays inside it. |
| 10 | Ethene is formed by elimination | Ethanol is a less polar solvent, so hydroxide takes a hydrogen and eliminates instead of substituting. |
04 What to do after marking
- After marking, redo only the wrong items and write down which step went wrong (formula, unit, or misread number).
- Repeat the same item two days later; move to the next paper only when both attempts are correct.
- Parents only need the answer and note columns; there is no need to explain every item.
Write “aqueous substitutes, ethanolic eliminates” on line one of your notes.Tutor Registration →
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