Reduce a nitrile to a primary amine
Reduce a nitrile with LiAlH₄ or H₂/Ni to form a primary amine while retaining the nitrile carbon.
A Level; Cambridge International Chemistry 9701, 2028–2030 syllabus, Topic 34. Use the stated reagents, conditions and product scope. Written practice is self-checked This online lesson cannot demonstrate supervised laboratory skills.
Before you begin
- Recall nucleophilic substitution, reduction, acyl-chloride addition–elimination, acid–base equilibria and covalent bonding.
Work on paper. Try each question before revealing help, and explain why your method works.
Quick readiness check
Which reagent pair can reduce a nitrile to a primary amine?
What you will learn
- Recall the two listed nitrile-reduction systems
- Retain the nitrile carbon in the amine chain
- Predict the primary amine product
Choose either listed reducing system
A nitrile can be reduced to a primary amine using LiAlH₄ or hydrogen with a nickel catalyst, H₂/Ni.
The nitrile carbon remains in the product and becomes the carbon bonded to NH₂: R–C≡N → R–CH₂NH₂.
Count the carbon at the nitrile end
Propanenitrile, CH₃CH₂C≡N, forms propan-1-amine, CH₃CH₂CH₂NH₂. The nitrile carbon is the third carbon in the amine chain.
Do not confuse nitrile reduction with hydrolysis to a carboxylic acid or with amide reduction. Name the reagent system given in the question.
Pause and explain
Does the carbon in C≡N remain in the amine product?
Worked example
Predict the product when ethanenitrile is reduced with H₂/Ni.
Show the worked solution
- Keep the nitrile carbon.
- Reduce C≡N to CH₂NH₂.
- Count the methyl carbon plus nitrile carbon.
Answer Ethylamine, CH₃CH₂NH₂.
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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.
Predict the product of CH₃CH₂C≡N reduction with LiAlH₄.
Give me a hint
Retain the nitrile carbon and convert the end group to CH₂NH₂.
Compare my reasoning
- The starting molecule contains three carbons including C≡N.
- The nitrile carbon becomes CH₂.
- Attach NH₂ at the chain end.
CH₃CH₂CH₂NH₂, propan-1-amine.
Look for these in your work
- Three carbons retained
- Primary amine
- Correct position
List both syllabus reduction methods for nitriles.
Give me a hint
One uses a complex hydride; the other uses hydrogenation.
Compare my reasoning
- LiAlH₄.
- H₂ with Ni catalyst.
- Either route forms a primary amine.
LiAlH₄ or H₂/Ni reduces a nitrile to a primary amine.
Look for these in your work
- LiAlH₄
- H₂/Ni
- Product class
A student says propanenitrile forms ethylamine because the nitrile carbon is ‘not part of the chain’. Correct the carbon count.
Give me a hint
The carbon in –C≡N is a carbon atom in the molecule.
Compare my reasoning
- CH₃CH₂C≡N has three carbons.
- Reduction keeps the nitrile carbon.
- The product is propan-1-amine.
Propanenitrile gives propan-1-amine; all three carbons, including the nitrile carbon, remain.
Look for these in your work
- Carbon count
- Nitrile carbon
- Product corrected
Common mistakes
- Losing the nitrile carbon
- Predicting an amide
- Using H₂/Pt when the listed catalyst is Ni
- Calling ethylamine methylamine
What can you explain now?
Which reagent pair can reduce a nitrile to a primary amine?
Compare with the explanation
H₂/Ni
Hydrogen with nickel is listed; LiAlH₄ is the other option.
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Make it stick
Which two reagent systems reduce nitriles, and what happens to the nitrile carbon?
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