Ester group (-COO-): The main functional group in tristearin is the ester group. Tristearin is a triglyceride, which means it is composed of three fatty acids esterified to a glycerol molecule. The ester group is formed by the reaction between the carboxylic acid group of the fatty acids and the hydroxyl group of glycerol.

Hydrocarbon chain (-CH2-CH2-CH2-): The fatty acids in tristearin are long-chain hydrocarbons. These hydrocarbon chains are nonpolar and hydrophobic, which means they repel water and are insoluble in water.

Methyl group (-CH3): The fatty acids in tristearin are also branched, with methyl groups attached to the hydrocarbon chain. These methyl groups contribute to the overall shape and structure of the tristearin molecule.

Triglyceride group: Tristearin is a triglyceride, which means it is composed of three fatty acids esterified to a glycerol molecule. The three fatty acids in tristearin are all stearic acid, which is a saturated fatty acid.