Esters

Uses of Esters

• Have characteristic sweet smells

• Used as food flavouring and perfumes

• Used as plasticisers to make them soft and flexible, but escape over time leaving the plastic stiff and brittle

• Used as solvents for polar organic molecules

Hydrolysis of Esters

• Esters undergo hydrolysis in acid or alkaline solution

• Hydrolysis is preferred in hot and alkaline conditions as the reaction is quicker

Alkaline Hydrolysis

• Leaders to formation of the sodium salt of the carboxylic acid and alcohol

• If excess of dilute H2SO4 or HCl is added to the sodium salt, then the carboxylic acid reforms

• Formation of sodium salts of long chain carboxylic acids is a useful product used in soaps

Acid Hydrolysis

• The reversal of the esterification reaction

Triglyceride Esters

• Triesters of fatty acids (long chain carboxylic acids) and glycerol

• Occur naturally as fats and oils

• Can undergo same hydrolysis as esters

Fats, properties

• Solid at room temperature and contain saturated acids

Oils, properties

• Liquids at room temperature and show some degree of unsaturation in the acid 

Alkaline conditions - triesters

• Leads to formation of glycerol and sodium salts of the long chain carboxylic acids used to make soap

• Lipid + 3KOH → glycerol + sodium salt

Acid conditions - triesters

• Form glycerol and the carboxylic acids