1. Unit 2
Section 2.7
Esters

2. Esters Ethanol + propanoic Acid Ethyl Propanoate + Water
A lot of carboxylic acids have horrible smells e.g. Butanoic acid in rancid butter, 3-methyl-2-hexenoic acid which is found in human sweat.
When these molecules react with alcohols they produce very pleasant smells. The fruity smells that are formed are called esters.
Alcohol + Carboxylic Acid Ester + Water
Ethanol + propanoic Acid Ethyl Propanoate + Water

3. Esterification The forward reaction is a condensation reaction
Esters are produced when carboxylic acids are heated with alcohols in the presence of an acid catalyst. The catalyst is usually concentrated sulphuric acid.
The forward reaction is a condensation reaction
The reverse reaction is a hydrolysis

4. Making Esters
Different combinations of alcohols and carboxylic acids make different smelling esters e.g. apple, pear etc.

5. Forming an ester is an example of a condensation reaction since two molecules are reacted together to produce a larger molecule plus water.
Uses of Esters
Apart from being used in perfumes, aftershaves and deodorants, esters are mainly used as solvents. They make good solvents as they are able to dissolve compounds not soluble in water e.g. nail varnish.