Composition of Fats and Oils:

Fats (solid) and oils (liquid) belong to a group of organic compounds called triesters or triglycerides.
They are formed from the condensation reaction of one glycerol (propane-1,2,3-triol) molecule and three fatty acid (long chained carboxylic acid) molecules.

Structural Formula of Glycerol:


The glycerol molecule contains a backbone of three carbon atoms with three hydroxyl or alcohol groups (-O-H) attached. Its condensed structural formula is CH2OHCHOHCH2OH.

Fatty Acids:
Fatty acids consist of the hydrocarbon chain (H and C atoms) with a carboxylic acid group (-COOH) at one end

When one glycerol molecule and three fatty acid molecules combine in a condensation reaction, one fat molecule (trigyceride) is formed and three molecules of water.


The equation below shows how a fat is formed. Notice how the H from the glycerol and the alcohol (-OH) group from the fatty acid are lost to form water. The process of forming a fat is called a condensation reaction. The bond formed between the glycerol and fatty acid molecules is called an ester or glycoside link. The reverse process is called hydrolysis.

VLObject-803-021205011214.gifGeneral formula of a Fat or an Oil