Making and Testing Esters – The Smell of Chemistry

Few experiments appeal to the senses quite like ester formation. When acids and alcohols react, they produce pleasant, fruity-smelling compounds called esters. From artificial flavours to perfumes and solvents, esters show how organic chemistry connects directly to everyday life.

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The Experiment

Students mix a carboxylic acid with an alcohol in the presence of an acid catalyst — usually concentrated sulfuric acid.

A simple school-level method involves:

1. Placing 1 cm³ of alcohol and 1 cm³ of carboxylic acid into a test tube.

2. Adding a few drops of concentrated sulfuric acid.

3. Gently warming the mixture in a water bath for a few minutes.

4. Pouring it into a beaker of water to smell the resulting ester (wafting carefully, not directly).

   

Common examples include:

Alcohol	Carboxylic Acid	Ester Formed	Characteristic Smell
Ethanol	Ethanoic acid	Ethyl ethanoate	Pear or nail polish remover
Methanol	Butanoic acid	Methyl butanoate	Pineapple
Pentanol	Ethanoic acid	Pentyl ethanoate	Banana

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The Science

The reaction is a condensation reaction, where two molecules combine and eliminate water:

$$\text{Alcohol} + \text{Carboxylic Acid} \rightarrow \text{Ester} + \text{Water}$$

Sulfuric acid acts as a catalyst and dehydrating agent, helping the equilibrium shift toward ester formation.

Students learn about reversible reactions, equilibrium position, and how structure determines smell.

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Skills Highlight

• Safely handling and heating volatile organic liquids

• Observing and describing qualitative results (odour, appearance)

• Understanding esterification as a reversible condensation reaction

• Linking molecular structure to real-world products in industry and biology

  

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Why It Works in Teaching

Making esters connects chemical theory with sensory experience. Students smell the result of their reaction and see chemistry as something tangible, memorable, and creative — a perfect example of applied organic chemistry.