Organic synthesis
Cambridge A-Level Chemistry (9701) · Unit 36: Organic synthesis (A Level) · 8 flashcards
Organic synthesis is topic 36.1 in the Cambridge A-Level Chemistry (9701) syllabus , positioned in Unit 36 — Organic synthesis (A Level) . In one line: The molecule contains a ketone (C=O) and an alkene (C=C) functional group.
Marked as A2 Level: examined at A Level in Paper 4 (A Level Structured Questions) and Paper 5 (Planning, Analysis and Evaluation). It is not tested on the AS-only papers (Papers 1, 2 and 3).
The deck below contains 8 flashcards — 3 definitions and 5 key concepts — covering the precise wording mark schemes reward. Use the 3 definition cards to lock down command-word answers (define, state), then move on to the concept and calculation cards to handle explain, describe, calculate and compare questions.
Identify the functional groups present in the following molecule: CH3CH2COCH2CH=CH2
The molecule contains a ketone (C=O) and an alkene (C=C) functional group.
What the Cambridge 9701 syllabus says
2025-2027 syllabus, in our words · A2 LevelWhat the syllabus expects you to be able to do in this topic, in plain English. For the exact wording, see the official syllabus (PDF).
- For an organic molecule with several functional groups: (a) identify its functional groups, using reactions from the syllabus; (b) predict its properties and reactions.
- Devise synthetic routes of more than one step to prepare organic molecules, using reactions from the syllabus.
- Analyse a given synthetic route, stating for each step the type of reaction and the reagents used, and identifying possible by-products.
Cambridge syllabus keywords to use in your answers
These are the official Cambridge 9701 terms tagged to this section. Mark schemes credit responses that use the exact term — weave them into your answers verbatim rather than paraphrasing.
Identify the functional groups present in the following molecule: CH3CH2COCH2CH=CH2
The molecule contains a ketone (C=O) and an alkene (C=C) functional group.
Name the reagents and conditions required to reduce a carboxylic acid to a primary alcohol.
The reagent required is Lithium Aluminium Hydride (LiAlH₄) in dry ether, followed by aqueous acid workup. This reduction is stronger than using NaBH₄.
Outline a multi-step synthetic route to convert ethanol to butanoic acid.
Step 1: Ethanol to bromoethane, using KBr + conc. H₂SO₄ (or PBr₃). Step 2: Heat bromoethane under reflux with KCN in ethanol to give propanenitrile (this adds one carbon). Step 3: Hydrolyse under reflux with dilute HCl to give propanoic acid. Step 4: Reduce with LiAlH₄ in dry ether to give propan-1-ol. Step 5: Convert to 1-bromopropane with KBr + conc. H₂SO₄ (or PBr₃). Step 6: Heat under reflux with KCN in ethanol to give butanenitrile. Step 7: Hydrolyse under reflux with dilute HCl to give butanoic acid.
What type of reaction is involved in converting an alcohol to an alkene using concentrated sulfuric acid?
This is an elimination reaction, specifically dehydration. The sulfuric acid acts as a dehydrating agent, removing water from the alcohol to form the alkene.
What reagents are required to convert a primary alcohol to an aldehyde?
Acidified Potassium Dichromate(VI) (K₂Cr₂O₇ / H⁺) with distillation to remove the aldehyde as it forms, preventing further oxidation to a carboxylic acid.
Identify the possible by-product(s) when reacting ethanol with excess concentrated sulfuric acid at 170°C.
The main organic by-product is diethyl ether, formed via intermolecular dehydration. Water is also produced. Polymerisation of ethene to form longer chain alkenes is another, minor possibility.
Describe the purpose of reflux in a chemical reaction.
Reflux allows a reaction to be heated at its boiling point for an extended period without loss of volatile reactants or products. This increases the reaction rate and yield.
Suggest a suitable reagent for converting a ketone to a secondary alcohol.
Sodium borohydride (NaBH₄) in ethanol is a suitable reducing agent. Alternatively, Lithium Aluminium Hydride (LiAlH₄) can be used, followed by dilute acid, but this is a stronger reducing agent and requires anhydrous conditions.
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