Esters: formation, properties and uses
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Explainer Video
Summary
Esters: formation, properties and uses
In a nutshell
Esters have the functional group . They are used in many products, such as in perfumes and solvents. Esters can undergo hydrolysis as well as other multiple types of reactions.
Equations
These are general chemical equations. You will need to be able to use these to write equations with specific substances.
Formation of esters
Esters have the functional group . They are formed by reacting an alcohol and carboxylic acid together in the presence of an acid catalyst, such as concentrated sulfuric acid.
Example
Uses of esters
Esters have many uses. Here are a few uses and properties that you need to know.
use | property |
| Food flavouring and perfumes | Esters have sweet smell making them an ideal ingredient to use in food and perfumes and enabling them to smell good. |
| Glue and printing ink | Esters are polar and soluble in many polar organic compounds. They also have low boiling points therefore evaporate easily, making them a good solvent. |
| Plasticiser | Esters make plastics more flexible. They are added to plastics during polymerisation. |
Hydrolysis
Hydrolysis is the breaking of a molecule using water. Esters can be hydrolysed in the presence of a catalyst to give a carboxylic acid (or carboxylate) and alcohol.
Acid hydrolysis
Ester is split in the presence of water and an acid catalyst, such as dilute sulfuric acid.
Example
Base hydrolysis
Ester can be split in the presence of water and a base catalyst, such as sodium hydroxide.
Example
Fats and oils
Fatty acids are long chains of carboxylic acids. They can be saturated or unsaturated.
Animal fat tends to have saturated hydrocarbon chains, allowing the molecules to pack closely together and increasing the number of Van der Waals forces. This leads to a higher melting point and hence why fats are solid at room temperature.
Vegetable oils have unsaturated hydrocarbon chains so the molecules are not able to pack closely together due to the presence of double bonds, creating kinks. This reduces the number of Van der Waals forces, hence a lower melting point. This is why they are liquids at room temperature.
Glycerol
Fatty acids join with glycerol to make esters.
Oils and fats can be hydrolysed to form glycerol and soap. This is done by heating fats and oils in the presence of sodium hydroxide.
Biodiesel
Vegetable oils are converted to biodiesel. This is done by reacting the vegetable oil with methanol in the presence of potassium hydroxide (catalyst). The result is glycerol and a mixture of methyl esters of fatty acids, which is biodiesel.
FAQs - Frequently Asked Questions
What are some uses of esters?
Esters are used in many products such as in perfumes, solvents and plasticisers.
How is biodiesel made?
Biodiesel is made by reacting the vegetable oil with methanol in the presence of potassium hydroxide.
What is the difference between animal fat and vegetable oil?
Animal fat tends to have saturated hydrocarbon chains, allowing the molecules to pack closely together. They are are solid at room temperature. Vegetable oils have unsaturated hydrocarbon chains so the molecules are not able to pack closely together. They are liquids at room temperature.