4.7 Esters

REVISION NOTES

IGCSE Edexcel Chemistry

4.7 Esters

4.7.1C Know that esters contain the functional group -COO-

The functional group of esters is

4.7.2C Know that ethyl ethanoate is the ester produced when ethanol and ethanoic acid react in the presence of an acid catalyst

ethanol + ethanoic acid → ethyl ethanoate (ester) + H2O

In the presence of an acid catalyst

4.7.3C Understand how to write the structural and displayed formulae of ethyl ethanoate

ETHYL ETHANOATE

Structural formula: CH₃COOCH₂CH₃
Displayed formula:

4.7.4C Understand how to write the structural and displayed formulae of an ester, given the name or formula of the alcohol and carboxylic acid from which it is formed and vice versa

Esterification

alcohol + carboxylic acid → ester + H2O

During esterification:
- H is lost from the alcohol
- OH is lost from the carboxylic acid
- The parts are combined to form ester

Identify the acid and alcohol part:
- Split the compound between two oxygens
- Acid: the half with C=O
- Alcohol: the half with O
Naming of ester:
- Count the number of carbons in both acid and alcohol part
- Alcohol part: -yl
- Carboxylic acid: -oate

4.7.5C Know that esters are volatile compounds with distinctive smells and are used as food flavourings and in perfumes

USES OF ESTERS

Esters are volatile compounds with distinctive smells
Ester are often used as food flavourings and in perfumes

4.7.6C Practical: prepare a sample of an ester such as ethyl ethanoate

METHODS

Mix ethanol, ethanoic acid and concentrated sulphuric acid in a round-bottom flask
Gently heat the mixture using a water bath or electric heater
- Bunsen burner cannot be used because ethanol is flammable
Ester formed is then distilled and collected to another beaker