Organic synthesis
Cambridge A-Level Chemistry (9701) · Unit 21: Organic synthesis · 8 flashcards
Organic synthesis is topic 21.1 in the Cambridge A-Level Chemistry (9701) syllabus , positioned in Unit 21 — Organic synthesis . In one line: The molecule contains two functional groups: an alkene (C=C) and a carboxylic acid (-COOH).
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 — 4 definitions and 4 key concepts — covering the precise wording mark schemes reward. Use the 4 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 molecule: CH3CH=CHCH2COOH
The molecule contains two functional groups: an alkene (C=C) and a carboxylic acid (-COOH).
What the Cambridge 9701 syllabus says
Official 2025-2027 spec · A2 LevelThese are the exact learning outcomes Cambridge sets for this topic. The candidate is expected to be able to do each of these on the relevant paper.
- for an organic molecule containing several functional groups: (a) identify organic functional groups using the reactions in the syllabus (b) predict properties and reactions
- devise multi-step synthetic routes for preparing organic molecules using the reactions in the syllabus
- analyse a given synthetic route in terms of type of reaction and reagents used for each step of it, and possible by-products Analysis
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.
Tips to avoid common mistakes in Organic synthesis
- › Sequence reactions carefully based on directing groups; -COOH is 3-directing, while -CH3 is 2,4-directing.
- › Work backwards: a hydroxynitrile is formed by nucleophilic addition of HCN to an aldehyde, which is formed by mild oxidation of a primary alcohol.
Identify the functional groups present in the molecule: CH3CH=CHCH2COOH.
The molecule contains two functional groups: an alkene (C=C) and a carboxylic acid (-COOH).
Describe a synthetic route to convert ethanol to ethanoic acid.
Ethanol can be oxidized to ethanoic acid in a two-step process. First, ethanol is oxidized to ethanal using acidified potassium dichromate(VI) with distillation to remove the aldehyde. Second, the ethanal is further oxidized to ethanoic acid using acidified potassium dichromate(VI) under reflux.
Propose reagents and conditions for converting but-2-ene to butan-2-ol.
But-2-ene can be converted to butan-2-ol by hydration. This requires steam (H₂O(g)) and an acid catalyst, such as concentrated H₃PO₄.
Outline the steps for converting benzene to nitrobenzene, then to phenylamine.
Step 1: Benzene to nitrobenzene requires nitration with concentrated nitric acid and concentrated sulfuric acid at 50-55°C. Step 2: Nitrobenzene to phenylamine requires reduction with tin and concentrated hydrochloric acid, followed by the addition of a base like NaOH.
What type of reaction is used to convert an alcohol to an alkene?
This conversion involves elimination. Specifically, it's dehydration, requiring concentrated sulfuric acid and heat, or passing the alcohol vapor over a hot aluminum oxide catalyst.
Starting with benzene, devise a synthetic route to produce 4-methylbenzoic acid.
1. Methylation of benzene: React benzene with chloromethane and AlCl3 (Friedel-Crafts alkylation) to form methylbenzene (toluene). 2. Oxidation of methylbenzene: Reflux methylbenzene with acidified potassium permanganate (KMnO4) or potassium dichromate(VI) to form 4-methylbenzoic acid.
What reagents are used to reduce a carboxylic acid to a primary alcohol?
Lithium aluminum hydride (LiAlH₄) in dry ether is used. Note: NaBH₄ is NOT strong enough to reduce carboxylic acids.
Give reagents and conditions to convert a primary alcohol to a haloalkane.
To convert a primary alcohol to a haloalkane, use concentrated hydrohalic acid (e.g. HCl, HBr) or phosphorus halides (PCl₅, PBr₃). Alternatively, SOCl₂ can be used to form a chloroalkane.
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