AQA A-Level Chemistry Paper 3, 2021: Question 30
1 mark · Medium difficulty · Multiple Choice
This question explores your understanding of organic synthesis and reaction pathways. You are asked to identify the correct intermediate compound, X, in the synthesis of propylamine from bromoethane. It requires knowledge of nucleophilic substitution reactions (to form a nitrile) and subsequent reduction (to form an amine).
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Question text
30 A two-step preparation of propylamine is shown.
bromoethane → X → propylamine
What is X?
[1 mark]
A CH3CH2CH2NH2
B CH3CH2CN
C CH3CH2CH2Br
D CH3CH2NH2
Mark scheme
Show the mark scheme
30 B 1 CH3CH2CN
How to answer it
Multiple Choice Explained: Intermediate in the Synthesis of Propylamine
Correct Answer: B – CH₃CH₂CN
Why? The two-step synthesis of propylamine from bromoethane involves:
- Nucleophilic substitution: Bromoethane reacts with KCN to give
CH₃CH₂CN(propanenitrile). - Reduction: The nitrile is reduced (e.g. by LiAlH₄ or catalytic hydrogenation) to give
CH₃CH₂CH₂NH₂(propylamine).
Why A is incorrect:
CH₃CH₂CH₂NH₂ is the final product, not the intermediate. This option skips over the actual intermediate in the process.
Why C is incorrect:
CH₃CH₂CH₂Br is not involved in the synthesis. Bromoethane (CH₃CH₂Br) is the starting material, not a longer-chain bromoalkane.
Why D is incorrect:
CH₃CH₂NH₂ is ethylamine, not propylamine. This would be the product of direct substitution with excess ammonia, which isn't the required synthetic route here.
Topics
Organic Chemistry · 3.3.14 Organic Synthesis
Question and mark scheme from the AQA A-Level Chemistry examination, Paper 3, 2021. QuestionVault is an independent revision resource; questions remain the copyright of the awarding body.