A Level · Cambridge (CIE) · 9701

Oxidise a secondary alcohol to a ketone

Distil a secondary alcohol with an acidified oxidising agent to obtain a ketone.

Carbonyl compounds · Cambridge 9701 AS Chemistry · 17.1

AS Level; Cambridge International Chemistry 9701, 2025–2027 syllabus. Distinguish aldehydes from ketones by structure and evidence; state reagent, condition and observation. Written practice is self-checked

Before you begin

Use carbonyl structures, alcohol oxidation and reduction from Topics 13 and 16, nucleophiles and curly arrows, and the organic reaction patterns from Topic 15.

Work on paper. Try each question before revealing help, and explain why your method works.

Quick readiness check

What product forms when a secondary alcohol is oxidised?

What you will learn

Recognise secondary alcohol oxidation
Use acidified oxidant and distillation
Locate the ketone carbonyl

Carbonyl reaction map. Primary alcohol oxidation by acidified dichromate(VI) or manganate(VII) with distillation gives an aldehyde; secondary alcohol oxidation gives a ketone. NaBH₄ or LiAlH₄ reduces either carbonyl to an alcohol. HCN with a KCN catalyst adds CN and OH across C=O to form a hydroxynitrile and adds one carbon.

A secondary alcohol gives a ketone

Heat a secondary alcohol with acidified K₂Cr₂O₇ or acidified KMnO₄ and distil to produce a ketone.

Propan-2-ol → propanone: CH₃CH(OH)CH₃ + [O] → CH₃COCH₃ + H₂O. The carbon that carried OH becomes the carbonyl carbon.

Use the structure to identify the product

The carbonyl carbon in a ketone is attached to two carbon groups. The carbon skeleton is retained while C–OH and a neighbouring C–H are oxidised to C=O.

Do not predict an aldehyde from a secondary alcohol. Tertiary alcohols do not oxidise under the syllabus conditions.

Pause and explain

Where is the C=O group in the product from butan-2-ol?

Put the idea to work

Worked example

Predict the product and conditions for oxidation of butan-2-ol.

Show the worked solution

The OH-bearing carbon has two carbon neighbours, so the alcohol is secondary.
Oxidation changes that carbon into C=O.
Distil the product with an acidified oxidising agent.

Answer Butan-2-ol + [O] → butan-2-one + H₂O; acidified K₂Cr₂O₇ or KMnO₄, heat and distil.

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From guided practice to a new situation

Write your answer and reasoning first. Use a hint only if you are stuck. The model solution is for self-checking; your written work is not automatically marked.

1 · Guided

Write the equation for oxidising cyclohexanol to cyclohexanone.

Give me a hint

Replace the C–OH site with C=O.

Compare my reasoning

Cyclohexanol is secondary.
The carbon skeleton remains a six-membered ring.
Use [O] and show water.

Cyclohexanol + [O] → cyclohexanone + H₂O; acidified K₂Cr₂O₇ or KMnO₄, heat and distil.

Look for these in your work

Ketone named
Ring preserved
Conditions stated

2 · Independent

What carbonyl product forms from pentan-3-ol?

Give me a hint

Locate the OH-bearing carbon before changing the functional group.

Compare my reasoning

The OH is at C3.
Oxidation keeps the C=O at C3.
The product is pentan-3-one.

Pentan-3-one.

Look for these in your work

Carbonyl position retained
Ketone named
Skeleton preserved

3 · Transfer

A student predicts pentanal from pentan-2-ol. Explain the error.

Give me a hint

Check whether the alcohol is primary or secondary.

Compare my reasoning

Pentan-2-ol has two carbon groups attached to its OH-bearing carbon.
It is secondary, not primary.
Oxidation gives pentan-2-one.

Pentan-2-ol is secondary and gives pentan-2-one; an aldehyde comes from a primary alcohol.

Look for these in your work

Alcohol class corrected
Product class corrected
Position retained

Common mistakes

Calling the product an aldehyde
Moving the carbonyl to a different carbon
Using a reducing agent

Recall without your notes

What can you explain now?

What product forms when a secondary alcohol is oxidised?

Compare with the explanation

A ketone

The OH-bearing carbon becomes an internal carbonyl carbon.

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Make it stick

How does the carbon bearing OH determine the ketone product from a secondary alcohol?

If you needed the solution, close it and solve the problem again from a blank page. A correct answer is stronger when you can explain the reason for each step.

Keep learning Chemistry

Check the official syllabus 2028–2030

Course scope and assessment

Four hundred and forty-two original lessons map the published learning outcomes across AS Chemistry Topics 1–22 and A Level Topics 23–37, with guided, independent and transfer practice and explained answers. Every numbered subject-content topic and listed outcome tag now has a mapped lesson sequence. Topic 32 maps all 12 hydroxy-compound outcome tags in 11 lessons; Topic 33 maps all 15 carboxylic-acid and derivative outcome tags in 16 lessons; Topic 34 maps all 22 nitrogen-compound outcome tags in 20 lessons; Topic 35 maps all 12 polymerisation outcome tags in 16 lessons; Topic 36 maps all four organic-synthesis outcome tags in 14 lessons; Topic 37 maps all 22 chromatography and NMR outcome tags in 18 lessons. Cambridge's 2028–2030 Version 1 syllabus states that there are no significant changes which affect teaching from the preceding edition; the routes are aligned to that edition. This is 37 of the 37 numbered subject-content topics. Full cumulative exam assessment, Paper 3 laboratory competence, Paper 5 investigation practice and human subject-teacher review remain outstanding. Written practice is self-checked and does not certify exam readiness.