Experiment 101

Objective

To prepare an ester (ethyl ethanoate) by reacting ethanol with acetic acid in the presence of concentrated sulfuric acid.

Introduction

Esters, which have characteristic sweet odors, can be synthesized by heating a carboxylic acid with an alcohol in the presence of a concentrated acid catalyst. In this experiment, acetic acid and ethanol react to form ethyl ethanoate, with sulfuric acid acting as a catalyst.

Reaction:

CH3​COOH + CH3​CH2​OH → CH3​COOCH2​CH3 ​+ H2​O

Materials

Chemicals

·       Ethanol

·       Acetic acid

·       Concentrated sulfuric acid (H₂SO₄)

Apparatus

·       Two test tubes

·       Two test tube holders

·       Dropper

Reagents

·       5 ml of acetic acid and 5 ml of ethanol in a test tube

·       1–2 drops of concentrated sulfuric acid

Procedure

1.    Place the acetic acid and ethanol mixture in a test tube.

2.    Secure the test tube in a holder.

3.    Add 1–2 drops of concentrated sulfuric acid to the mixture.

4.    Heat the test tube for 5–6 minutes using a Bunsen burner.

5.    Stop heating once a sweet odor is detected, indicating ester formation.

Observation

A distinct sweet smell is observed, characteristic of the ester ethyl ethanoate.

Questions

1.    What is an ester?

2.    How is an ester formed?

3.    Why is an acid catalyst needed for ester formation?