A Level · Cambridge (CIE) · 9701

Add hydrogen cyanide to a ketone

Add CN and OH across a ketone C=O to form a hydroxynitrile and extend the carbon count.

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

Which product functional groups form in HCN addition to a ketone?

What you will learn

Predict a ketone hydroxynitrile
Use HCN, KCN catalyst and heat
Count all product carbons

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.

The ketone carbonyl carbon becomes tetrahedral

HCN adds across a ketone C=O with KCN catalyst and heat. CN attaches to the carbonyl carbon, and the oxygen becomes OH after proton transfer.

Propanone forms 2-hydroxy-2-methylpropanenitrile: (CH₃)₂CO + HCN → (CH₃)₂C(OH)CN. The product contains four carbons because the CN carbon is included.

Substitution pattern affects the product

A ketone carbonyl carbon is attached to two carbon groups, so the product OH and CN are attached to that same carbon. Keep both original groups and add the nitrile carbon.

Use the specified HCN, KCN catalyst and heat. The reaction does not break the carbon skeleton around the carbonyl carbon.

Pause and explain

Where do CN and OH attach in ketone HCN addition?

Put the idea to work

Worked example

Write and name the product when butan-2-one reacts with HCN.

Show the worked solution

Retain the four-carbon chain.
Add CN to the carbonyl carbon and change C=O to C–OH.
Include the nitrile carbon in the product parent.

Answer CH₃COCH₂CH₃ + HCN → CH₃C(OH)(CN)CH₂CH₃; 2-hydroxy-2-methylbutanenitrile, KCN catalyst and heat.

Try a topic test

Choose Easy, Normal or Difficult. Save your answers and open worked review after finishing.

Test this topic →

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

Predict the product and name from pentan-3-one plus HCN.

Give me a hint

Add CN and OH to carbon 3 and count the nitrile carbon.

Compare my reasoning

The pentanone chain contains five carbons.
The CN carbon makes six in the product.
The former C3 carbon is C2 when numbering from nitrile.

2-hydroxy-2-ethylbutanenitrile; HCN, KCN catalyst and heat.

Look for these in your work

Groups added correctly
Nitrile carbon counted
Name based from nitrile end

2 · Independent

A proposed product from propanone is CH₃CH(OH)CN. What ketone substituents were lost?

Give me a hint

Compare the starting carbonyl carbon's two methyl groups.

Compare my reasoning

Propanone has two methyl groups bonded to C=O.
Both remain attached after addition.
The correct product is (CH₃)₂C(OH)CN.

The proposed formula loses one methyl group; retain both to give (CH₃)₂C(OH)CN.

Look for these in your work

Starting structure inspected
Substituent loss identified
Product corrected

3 · Transfer

How many carbons are in the hydroxynitrile from butanone, and why?

Give me a hint

Include the carbon inside –C≡N.

Compare my reasoning

Butanone contributes four carbon atoms.
HCN adds one carbon as the nitrile group.
The product has five carbons.

Five carbons: the four from butanone plus the carbon in CN.

Look for these in your work

Starting count correct
CN carbon included
Total stated

Common mistakes

Dropping one of the ketone's carbon groups
Forgetting the nitrile carbon in the name
Putting OH on a neighbouring carbon

Recall without your notes

What can you explain now?

Which product functional groups form in HCN addition to a ketone?

Compare with the explanation

A hydroxyl and a nitrile

The former carbonyl carbon gains OH and CN.

After trying it yourself, choose your next review. This is your self-assessment.

Your review choice appears on Today. Sign in to sync it across devices.

Continue to next lesson Back to Today

Make it stick

How do the two ketone substituents and the nitrile carbon appear in a hydroxynitrile product?

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.