AQA A-Level Chemistry Paper 3, 2023: Question 31

1 mark · Hard difficulty · Multiple Choice

Conversion of Compound X to Alcohol This question focuses on identifying compound X, which undergoes a two-stage chemical reaction. The process involves treatment with concentrated H₂SO₄ to form an intermediate, followed by hydrolysis with excess H₂O to produce an alcohol. Understanding reaction pathways for alkenes, aldehydes, or amides is key.

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Question

AQA A-Level Chemistry Paper 3, 2023: Question 31
Question text

31 Compound X can be converted into an alcohol in a two-stage process.

What is the name of compound X?

[1 mark]

A propene

B propanal

C methylbenzene

D ethanamide

Mark scheme

Show the mark scheme Mark scheme for AQA A-Level Chemistry Paper 3, 2023: Question 31

31 A 1 (AO2) propene

How to answer it

Conversion of Compound X to Alcohol

Question:

Compound X can be converted into an alcohol in a two-stage process:

Step 1: Reaction with concentrated H2SO4 to form an intermediate.
Step 2: Hydrolysis with excess H2O to form the alcohol.

What is the name of compound X ?

  • A: propene
  • B: propanal
  • C: methylbenzene
  • D: ethanamide

Correct Answer: A

propene is the correct answer. The conversion of propene to an alcohol involves the formation of an intermediate through electrophilic addition with concentrated H2SO4, followed by hydrolysis with water.

Explanation:

The reaction mechanism is as follows:

  1. In the first step, propene reacts with concentrated H2SO4, undergoing electrophilic addition to form a hydrogen sulfate intermediate.
  2. In the second step, hydrolysis of the intermediate with excess water breaks the sulfate group, yielding an alcohol (propan-2-ol in this case).

The other options do not fit the reaction sequence:

  • B: Propanal would not undergo these reactions to form an alcohol.
  • C: Methylbenzene (toluene) does not form an alcohol via this mechanism.
  • D: Ethanamide does not react in this manner to produce an alcohol.
Teacher Tip: Highlight the electrophilic addition mechanism in class and explain how propene reacts with sulfuric acid to form an intermediate, followed by hydrolysis.

Topics

Organic Chemistry · 3.3.14 Organic Synthesis

Question and mark scheme from the AQA A-Level Chemistry examination, Paper 3, 2023. QuestionVault is an independent revision resource; questions remain the copyright of the awarding body.