Esterification
Summary: Esterification is the condensation reaction between a carboxylic acid and an alcohol to form an ester and water. It is catalysed by concentrated sulfuric acid (H₂SO₄) and is heated under reflux. Esters have characteristic fruity smells. Tags: igcse chemistry definition organic-chem Created: 2026-07-14 Last Updated: 2026-07-23
Esterification is the reaction between a carboxylic acid and an alcohol to produce an ester and water. It is a type of condensation reaction (water is eliminated).
General Equation
Carboxylic acid + Alcohol ⇌ Ester + Water
R—COOH + HO—R’ ⇌ R—COO—R’ + H₂O
(where R and R’ represent alkyl chains)
Specific Example (IGCSE)
Ethanoic acid + Ethanol ⇌ Ethyl ethanoate + Water
CH₃COOH + C₂H₅OH ⇌ CH₃COOC₂H₅ + H₂O
Conditions
| Condition | Details |
|---|---|
| Catalyst | Concentrated sulfuric acid (H₂SO₄) — a few drops |
| Temperature | Warm (heated under reflux for ~30 min) |
| Process | Reflux (vapours condense and return to the flask) |
The sulfuric acid catalyst:
- Speeds up the reaction
- Also acts as a dehydrating agent — removes water, shifting equilibrium to produce more ester
Why Is It a Condensation Reaction?
Esterification is a condensation reaction because:
- Two molecules combine
- A small molecule (water) is eliminated
- The —OH from the carboxylic acid and —H from the alcohol’s —OH group combine to form H₂O
Identifying the Products
The ester name comes from:
- First part: from the alcohol (e.g. “ethyl” from ethanol)
- Second part: from the carboxylic acid (e.g. “ethanoate” from ethanoic acid)
| Alcohol | Acid | Ester |
|---|---|---|
| Methanol | Ethanoic acid | Methyl ethanoate |
| Ethanol | Methanoic acid | Ethyl methanoate |
| Ethanol | Propanoic acid | Ethyl propanoate |
Properties and Uses of Esters
- Fruity/pleasant smells — used as flavourings and fragrances
- Volatile — evaporate easily, which makes them good solvents
- Used in perfumes, food flavouring, and as industrial solvents
Key Facts
- Esterification: carboxylic acid + alcohol → ester + water
- Catalyst: concentrated H₂SO₄ (also dehydrating agent)
- This is a condensation reaction (water eliminated)
- Esters have fruity smells — used as flavourings and fragrances
- Reaction is reversible (equilibrium, ⇌)
- Name: alkyl (from alcohol) + alkanoate (from acid)
See Also
- Esters
- Carboxylic Acids
- Alcohols
- Condensation Reaction
- Organic Chemistry Fundamentals
- IGCSE-Chem-Index
This is a key term definition page — part of the IGCSE Chemistry (0620/0971) keyword glossary.