AQA A-Level Chemistry Paper 3, 2023: Question 32

1 mark · Medium difficulty · Multiple Choice

Oxidation of 1-Phenylethanol This question asks for the correct balanced equation representing the oxidation of 1-phenylethanol. The process involves an oxidising agent, indicated by [O], and the products depend on whether the alcohol is oxidised to an aldehyde, ketone, or carboxylic acid. Understanding primary and secondary alcohol oxidation reactions is crucial.

Practise this question

Question

AQA A-Level Chemistry Paper 3, 2023: Question 32

Question text

32 Which is a correct equation for the oxidation of 1-phenylethanol?

[O] represents oxygen from an oxidising agent.

[1 mark]

A C6H5CH2CH2OH + 2[O] → C6H5CH2COOH + H2O

B C6H5CH2CH2OH + [O] → C6H5CH2CHO + H2O

C C6H5CH(OH)CH3 + [O] → C6H5CH2CHO + H2O

D C6H5CH(OH)CH3 + [O] → C6H5COCH3 + H2O

Mark scheme

Show the mark scheme

Mark scheme for AQA A-Level Chemistry Paper 3, 2023: Question 32

32 D 1 (AO1) C6H5CH(OH)CH3 + [O] → C6H5COCH3 + H2O

How to answer it

Oxidation of 1-Phenylethanol

Question

Which is a correct equation for the oxidation of 1-phenylethanol? [O] represents oxygen from an oxidising agent.

A: C₆H₅CH₂CH₂OH + 2[O] → C₆H₅CH₂COOH + H₂O
B: C₆H₅CH₂CH₂OH + [O] → C₆H₅CH₂CHO + H₂O
C: C₆H₅CH(OH)CH₃ + [O] → C₆H₅CH₂CHO + H₂O
D: C₆H₅CH(OH)CH₃ + [O] → C₆H₅COCH₃ + H₂O

Correct Answer: D

The correct equation is:

C₆H₅CH(OH)CH₃ + [O] → C₆H₅COCH₃ + H₂O

This represents the oxidation of the secondary alcohol 1-phenylethanol to a ketone (acetophenone).

Explanation

Key points about the oxidation:

1-Phenylethanol ( C₆H₅CH(OH)CH₃ ) is a secondary alcohol.
Secondary alcohols are oxidised to ketones using an oxidising agent such as potassium dichromate (K₂Cr₂O₇) in acidified conditions.
The product is acetophenone ( C₆H₅COCH₃ ) and water.

Why Other Options Are Incorrect

A: This equation represents the oxidation of a primary alcohol, which is not the structure of 1-phenylethanol.
B: This equation also applies to a primary alcohol, not a secondary alcohol like 1-phenylethanol.
C: The equation implies oxidation to an aldehyde, but secondary alcohols are oxidised to ketones, not aldehydes.

Final Answer

The correct equation for the oxidation of 1-phenylethanol is:

D: C₆H₅CH(OH)CH₃ + [O] → C₆H₅COCH₃ + H₂O

Topics

Organic Chemistry · 3.3.5 Alcohols

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.