Making Esters in Test Tubes

Materials: ★★☆ Available in most school laboratories or specialist stores
Difficulty: ★★☆ Can be done by science teachers
Safety: ★★☆ Some safety precautions required to perform safely

Categories: Organic Chemistry

Alternative titles: Ester Synthesis Lab

Summary

Alcohols and carboxylic acids react in the presence of sulfuric acid to form esters and water. Many esters have strong, pleasant odors and are commonly used in perfumes and artificial flavorings.

Procedure

Prepare a data table listing which alcohols and carboxylic acids will be combined, leaving space for observations.
Put on safety goggles and ensure the workspace is free of open flames.
Prepare a hot-water bath in a beaker using a hot plate (not a Bunsen burner).
In a clean test tube, add about 20 drops of an alcohol, followed by ~0.1 g or 60 drops of a carboxylic acid.
Carefully add 2 drops of concentrated sulfuric acid (catalyst).
Record observations of the reactants.
Place the test tube in the hot-water bath using a clamp and heat for about 5 minutes.
After heating, carefully pour the mixture into an Erlenmeyer flask with water to help detect the scent.
Repeat the process with different combinations of alcohols and carboxylic acids.
Record the odors of the resulting esters.
Dispose of all products as instructed and wash hands thoroughly.

Links

NECT Gr 12 Making Esters - Jo-Anne Miles-Levet:

📄 Ester Synthesis Lab - The University of Akron: https://www.uakron.edu/polymer/agpa-k12outreach/lesson-plans/pdf/wagner-worksheet1.pdf

Variations

Try using different alcohol–acid combinations to produce additional esters with unique scents.
Compare the scents of synthetic esters to natural fruit or plant aromas.
Explore how reaction time or heating conditions affect the strength of ester odor.

Safety Precautions

Always wear goggles throughout the experiment.
Handle concentrated sulfuric acid with extreme care; it is highly corrosive.
Avoid inhaling vapors directly from test tubes.
Use only a hot plate for heating—do not use open flames.
Wash hands thoroughly after handling chemicals.

Questions to Consider

What functional group is present in all alcohols? (-OH group)
What functional group is present in all carboxylic acids? (-COOH group)
What functional group is characteristic of esters? (-COOR group)
Why is sulfuric acid added to the reaction? (It acts as a catalyst and dehydrating agent, driving the equilibrium toward ester formation.)
Isobutyl alcohol and formic acid produce a raspberry scent. What is the name of the ester? (Isobutyl formate).