Make esters from carboxylic acids and alcohols
Esterification combines a carboxylic acid and an alcohol; concentrated sulfuric acid acts as catalyst.
AS Level; Cambridge International Chemistry 9701, 2025–2027 syllabus. Track the carbon skeleton, name reagents and conditions, and show products and observations. Written practice is self-checked
Before you begin
- Use alcohol oxidation and carbonyl chemistry from Topics 16–17, functional-group names, acid–base equations and balanced reaction formulae.
Work on paper. Try each question before revealing help, and explain why your method works.
Quick readiness check
Which reagent acts as the catalyst in the syllabus esterification?
What you will learn
- Name the two reactants
- Use concentrated sulfuric acid as catalyst
- Name the ester from both carbon fragments
Esterification combines acid and alcohol
A carboxylic acid reacts with an alcohol to form an ester and water. Concentrated H₂SO₄ acts as catalyst; warming the mixture helps the reaction proceed.
RCOOH + R′OH ⇌ RCOOR′ + H₂O. The acid contributes the alkanoate part of the ester name; the alcohol contributes the alkyl part.
Read the name from the structure
Ethanoic acid plus propan-1-ol forms propyl ethanoate and water.
Esterification and ester hydrolysis are opposite functional-group changes. The catalyst is concentrated sulfuric acid; it is not the ester reactant.
Pause and explain
What two organic reactants form an ester by esterification?
Worked example
Name the ester formed from butanoic acid and ethanol.
Show the worked solution
- The acid contributes butanoate.
- Ethanol contributes ethyl.
- Put the alcohol-derived alkyl name first.
Answer Ethyl butanoate and water; concentrated H₂SO₄ is the catalyst.
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.
What ester forms from propanoic acid and methanol?
Give me a hint
Use the alcohol-derived alkyl part first.
Compare my reasoning
- Methanol contributes methyl.
- Propanoic acid contributes propanoate.
- Combine the names and include water as a product.
Methyl propanoate and water; concentrated H₂SO₄ catalyst.
Look for these in your work
- Alkyl part correct
- Acid-derived part correct
- Catalyst/products stated
Name the organic reactants needed to prepare ethyl ethanoate.
Give me a hint
Split the ester name into alkyl and alkanoate parts.
Compare my reasoning
- Ethyl comes from ethanol.
- Ethanoate comes from ethanoic acid.
- Use concentrated H₂SO₄ as catalyst.
Ethanol and ethanoic acid, with concentrated H₂SO₄ catalyst.
Look for these in your work
- Alcohol identified
- Acid identified
- Catalyst recalled
A student writes propanoic acid + ethanol → ethyl propanoate + H₂. Correct the products.
Give me a hint
Esterification is not metal displacement.
Compare my reasoning
- The ester product name is ethyl propanoate.
- The acid and alcohol lose the elements of water.
- Write H₂O, not H₂.
Propanoic acid + ethanol ⇌ ethyl propanoate + H₂O; concentrated H₂SO₄ catalyst.
Look for these in your work
- Ester named
- Water corrected
- Catalyst included
Common mistakes
- Reversing alkyl and alkanoate in the name
- Calling sulfuric acid the ester reactant
- Forgetting water
What can you explain now?
Which reagent acts as the catalyst in the syllabus esterification?
Compare with the explanation
Concentrated H₂SO₄
Concentrated sulfuric acid catalyses the reaction.
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.
Make it stick
How do you identify each part of an ester name, and what role does concentrated sulfuric acid play?
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.