Esterify an alcohol with a carboxylic acid
Use concentrated sulfuric acid catalyst to form an ester and water from an alcohol and acid.
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 are the products of alcohol plus carboxylic acid in esterification?
What you will learn
- Recall esterification conditions
- Name ester products from both reactants
- Recognise reversible condensation
Join the alcohol and carboxylic acid parts
An alcohol reacts with a carboxylic acid in a condensation reaction to form an ester and water. Concentrated H₂SO₄ acts as a catalyst; ethanol is the syllabus example.
Ethanol + ethanoic acid ⇌ ethyl ethanoate + water. The alkyl name comes from the alcohol; the carboxylic-acid part supplies the alkanoate name.
Track the groups across the ester link
The O from the alcohol remains in the –COO– ester link, while an H from the alcohol and OH from the acid form water in the simple condensation picture.
The reaction is reversible under acid-catalysed conditions. Do not confuse esterification with ester hydrolysis; hydrolysis uses water to split the ester and can run under dilute acid or alkali with heat.
Pause and explain
Which catalyst is used in the syllabus alcohol–acid esterification?
Worked example
Name the ester formed when propan-1-ol reacts with butanoic acid.
Show the worked solution
- The alcohol gives the propyl group.
- The acid gives the butanoate part.
- Use concentrated H₂SO₄ catalyst and show water.
Answer Propan-1-ol + butanoic acid ⇌ propyl butanoate + H₂O; concentrated H₂SO₄ catalyst.
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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.
Give the products when ethanol reacts with propanoic acid and state the catalyst.
Give me a hint
Name the alcohol-derived alkyl group first.
Compare my reasoning
- Ethanol gives ethyl.
- Propanoic acid gives propanoate.
- Water is also formed.
Ethanol + propanoic acid ⇌ ethyl propanoate + H₂O; concentrated H₂SO₄ catalyst.
Look for these in your work
- Ester name correct
- Water included
- Catalyst stated
Name the reactants needed to prepare methyl ethanoate by esterification.
Give me a hint
Read the ester name as alkyl from the alcohol plus carboxylate from the acid.
Compare my reasoning
- Methyl comes from methanol.
- Ethanoate comes from ethanoic acid.
- Use concentrated sulfuric acid catalyst.
Methanol and ethanoic acid; concentrated H₂SO₄ catalyst.
Look for these in your work
- Alcohol identified
- Acid identified
- Catalyst stated
A student calls the reaction of ethanol with ethanoic acid hydrolysis. Correct the term and distinguish the reverse process.
Give me a hint
Check whether water is a product or a reactant.
Compare my reasoning
- Esterification forms water and an ester.
- Hydrolysis uses water to cleave an ester.
- Use the direction and reactants to select the name.
It is esterification (condensation); ester hydrolysis uses water and produces an alcohol plus acid or carboxylate.
Look for these in your work
- Reaction named
- Water role distinguished
- Products compared
Common mistakes
- Reversing the alcohol and acid-derived name parts
- Omitting water
- Naming dilute acid as the esterification catalyst
What can you explain now?
What are the products of alcohol plus carboxylic acid in esterification?
Compare with the explanation
An ester and water
This is a condensation reaction that forms an ester link.
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Make it stick
How do the alcohol and carboxylic acid determine the two parts of an ester name?
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.