Hydrolyse an ester to make an alcohol
Use dilute acid or dilute alkali and heat; identify the alcohol and the acid-side product.
AS Level; Cambridge International Chemistry 9701, 2025–2027 syllabus. State reagents and conditions, follow the stated reaction pathway, and distinguish each alcohol class and oxidation product. Written practice is self-checked
Before you begin
- Use functional-group formulae and reaction types from Topic 13, alkene reactions from Topic 14, and halogenoalkane substitution from Topic 15.
Work on paper. Try each question before revealing help, and explain why your method works.
Quick readiness check
What does ester hydrolysis produce on the alcohol side?
What you will learn
- Recall ester hydrolysis conditions
- Predict the alcohol product
- Distinguish acidic and alkaline hydrolysis products
Break the ester link
Hydrolysis uses water to cleave the ester functional group. With dilute acid and heat, an ester forms an alcohol and a carboxylic acid; the reaction is reversible.
For ethyl ethanoate, acidic hydrolysis gives ethanol and ethanoic acid: CH₃COOCH₂CH₃ + H₂O ⇌ CH₃COOH + CH₃CH₂OH.
Alkaline hydrolysis gives a carboxylate
Dilute alkali and heat hydrolyse an ester to an alcohol and a carboxylate salt. For ethyl ethanoate with NaOH, the organic products are ethanol and sodium ethanoate.
The alcohol comes from the alkyl side attached through oxygen. Do not report a carboxylic acid as the direct product of alkaline hydrolysis unless an acidification step is specified.
Pause and explain
What is the direct acid-side product of alkaline ester hydrolysis?
Worked example
Give the products of acidic hydrolysis of methyl propanoate.
Show the worked solution
- Break the ester bond between the acyl and alkoxy parts.
- The alkoxy side becomes methanol.
- The acyl side becomes propanoic acid in dilute acid.
Answer CH₃CH₂COOCH₃ + H₂O ⇌ CH₃CH₂COOH + CH₃OH; dilute acid, heat.
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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.
Predict the products of acidic hydrolysis of propyl methanoate.
Give me a hint
The alkoxy side gives the alcohol; the acyl side gives the acid.
Compare my reasoning
- The propyl group attached through oxygen becomes propanol.
- The methanoate side becomes methanoic acid.
- State dilute acid and heat.
Propyl methanoate + H₂O ⇌ propanol + methanoic acid; dilute acid, heat.
Look for these in your work
- Alcohol side identified
- Acid side identified
- Conditions stated
Predict the organic products when ethyl ethanoate is heated with dilute NaOH.
Give me a hint
Alkaline hydrolysis forms a carboxylate salt.
Compare my reasoning
- The ethoxy group forms ethanol.
- The ethanoate side forms sodium ethanoate.
- Do not write ethanoic acid without an acidification step.
Ethanol and sodium ethanoate.
Look for these in your work
- Alcohol correct
- Carboxylate correct
- Conditions interpreted
A student writes methanol from ethyl ethanoate. Explain the mismatch.
Give me a hint
Follow the alkyl group bonded to the ester oxygen.
Compare my reasoning
- Ethyl ethanoate has –OCH₂CH₃.
- That alkoxy fragment becomes ethanol.
- Methanol would come from a methyl ester.
Ethyl ethanoate gives ethanol; the alkyl group attached to the ester oxygen determines the alcohol.
Look for these in your work
- Ester fragment located
- Alcohol corrected
- Methyl/ethyl distinction explained
Common mistakes
- Swapping the alcohol and carboxylic-acid parts
- Omitting water from the hydrolysis equation
- Writing a carboxylate as a carboxylic acid in alkaline conditions
What can you explain now?
What does ester hydrolysis produce on the alcohol side?
Compare with the explanation
An alcohol
The alkoxy side of the ester becomes an alcohol.
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Make it stick
How does the carboxyl-side product differ between acidic and alkaline ester hydrolysis?
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.