Esters: Formation & Uses

Instructor: Sarah Pierce

Sarah has a doctorate in chemistry, and 12 years of experience teaching high school chemistry & biology, as well as college level chemistry.

This lesson describes the uses and structure of esters. The mechanism of ester formation is described, as well as biological applications, such as saponification and the synthesis of biodiesel.

What is an Ester?

When you bite into a banana flavored Laffy Taffy, banana flavoring that doesn't exactly taste like bananas fills your mouth. Have you ever wondered what that flavoring is? Turns out it is a chemical compound called an ester, specifically isoamyl acetate.

Isoamyl acetate is the ester responsible for banana flavoring
Isoamyl acetate

Esters are organic molecules that contain a R-COO-R' functional group. Another way to think about this is that an ester functional group has a carbonyl group and an oxygen group next to each other. Remember, R just stands for the rest of the molecule and is a hydrocarbon chain. The ester functional group will never be at the end of a molecule. It will always be in the middle.

The ester functional group

How are Esters Made?

Esters are made when a molecule with an alcohol functional group and a molecule with a carboxylic acid functional group react in a process called esterfication or Fischer esterfication. This reaction also uses a strong acid catalyst such as sulfuric acid.

When an alcohol and a carboxylic acid molecule reaction, they form an ester

Where are Esters Found?

Have you ever wondered why perfume smells so good? It's because it contains ester molecules! Esters are found in food flavorings, perfumes, and in biological molecules such as triglycerides. Esters can also be used to make products such as soap and biodiesel.


When you get your lipids checked at the doctor, they are measuring the amount of triglycerides, a biological ester.

Triglycerides are biological esters

Animal fats, like butter, and plant oils, like coconut oil, are triglycerides as well. They are formed when glycerol reacts with three fatty acid molecules to form three ester bonds. If the triglyceride is a solid at room temperature, it is called a fat. If the triglyceride is a liquid at room temperature, it is called an oil.

A triglyceride forms when a glycerol molecule reacts with three fatty acid molecules, forming an ester functional group
triglyceride synthesis

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